(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Transactions of the Royal Society of Edinburgh"

HUBS 




6-9 



TRANSACTIONS 



OF THE 



EOYAL SOCIETY OF EDINBUKGH 



/S\ k- 



d.df. 



TRANSACTIONS 



OF THB 



EOYAL SOCIETY 



OF 



EDINBURGH. 



VOL. XXXV. 




EDINBURGH: 

PUBLISHED BY ROBERT GRANT & SON, 107 PRINCES STREET, 
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, CO VENT GARDEN, LONDON. 



MDCCCXC. 



Part I. published . . . January 21, 1889. 

Part IT. „ ... March 10, 1890. 

Part III. „ . February 3, 1890. 

Part IV. „ ... April 23, 1890. 



CONTENTS. 



PART I. (1887-88.) 

NUMBER PAOK 

I. On the Number of Dust Particles in the Atmosphere. By John 

Aitken, Esq. (With a Plate), .... 1 

II. The History of Volcanic Action during the Tertiary Period in the 
British Isles. By Archibald Geikie, LL.D., F.R.S., Director 
General of the Geological Survey of the United Kingdom. 
(With Two Maps and Fifty three Woodcuts), . . 21 

III. Mean Scottish Meteorology for the last Thirty-tivo Years. By 

C. Piazzi Smyth, late Astronomer-Royal for Scotland, and 
F.RS.E., F.R.A.S., &c. (With Fourteen Plates), . . 185 

IV. Eight Years' Observations of the New Earth Thermometers at the 

Royal Observatory, Edinburgh, 1879-1888. By C. Piazzi 
Smyth, late Astronomer-Royal for Scotland, and F.R.S.E., 
F.R.A.S., &c. (With Four Plates), . . . 287 

V. On Neuropteris plicata, Sternberg, and Neuropteris rectinervis, 
Kidston, n. sp. By Robert Kidston, F.R.S.E., F.G.S. (With 
a Plate), ....... 313 

VI. On the Fossil Flora of the Staffordshire Coal Fields. By Robert 

Kidston, F.R.S.E., F.G.S. (With a Plate), . . .317 

VII. Experimental Researches in Mountain Building. By Henry M. 
Cadell, Esq. of Grange, B.Sc, F.R.S.E., H.M. Geological 
Survey of Scotland. (With Thirty-six Illustrations), . . 337 



vi CONTENTS. 



PART II. (1887-89.) 

M'MBBR PAGE 

VIII. Histological Observations on the Muscular Fibre and Connective 
Tissue of the Uterus during Pregnancy and the Puerperium. 
By T. Arthur Helme, M.B. (With a Plate), . . 359 

IX. On some Relations between Magnetism and Twist in Iron and 
Nickel. Part I. By Cargill G. Knott, D.Sc. (Edin.), 
F.R.S.E., Professor of Physics, Imperial University, Tokyo, 
Japan, ....... 377 

X. On the Fossil Plants in the Ravenhead Collection in the Free 
Library and Museum, Liverpool. By Robert Kidston, 
F.R.S.E., F.G.S. (Plates I. and II.), . . .391 

XL On some Fossil Plants from Teilia Quarry, Gwaenysgor, near 
Prestatyn, Flintshire. By Robert Kidston, F.R.S.E., F.G.S. 
(With Two Plates), . . . . . .419 

XII. On the Behaviour of the Hydrates and Carbonates of the Alkali- 
Metals, and of Barium, at High Temperatures, and on the 
Properties of Lithia and the Atomic Weight of Lithium. By 
Professor W. Dittmar, ..... 429 

XIII. On the Determination of the Curve, on one of the Coordinate 

Planes, which forms the Outer Limit of the Positions of the 
Point of Contact of an Ellipsoid of Revolution which always 
touches the three Planes of Reference. By G. Plarr, Docteur 
es-sciences, . . . . . . .471 

XIV. On Ostracoda collected by H. B. Brady, Esq., LL.D., F.R.S., in 

the South Sea Islands. By George Stewardson Brady, 
M.D., LL.D., F.R.S. (Plates I.-IV.), . . .489 

XV. On Benzyl Phosphines and their Derivatives. By Professor 
Letts and R. F. Blake, Esq., Queen's College, Belfast. 
(With a Plate), ...... 527 

XVI. On the Anatomy, Histology, and Affinities of Phreoryctes. By 
Frank E. Beddard, M.A., Prosector to the Zoological Society 
of London, and Lecturer on Biology at the Medical School 
of Guy's Hospital. (With a Plate), . . . .629 



CONTENTS. Vll 

NUMBKR PAGE 

XVII. On the Placentation of Halicore Dugong. By Sir William 
Turner, M.B., LL.D., D.C.L., F.RSS.L. and E., Professor 
of Anatomy in the University of Edinburgh. (Plates L, II., 
Ill), 641 

XVIII. Non-Alternate ± Knots, of Orders Eight and Nine. By C. N. 

Little, of Nebraska State University. (With a Plate), . 663 



PART III. (1887-89.) 

XIX. On the Development and Life- Histories of the Teleostean Food- 
and other Fishes. By Professor W. C. M'Intosh, F.R.S., 
and E. E. Prince, B.A., St Andrews Marine Laboratory. 
(Plates I.-XX VIII.), 665 



PART IV. (1889-1890.) 

XX. On the Thermal Conductivity and Specific Heat of Manganese- 
Steel. By A. Crichton Mitchell, B.Sc., . . . 947 

XXI. Strophanthus hispidus : its Natural History, Chemistry, and 
Pharmacology. By Thomas R. Fraser, M.D., F.R.S., 
F.R.S.E., F.R.C.P.E., Professor of Materia Medica in the 
University of Edinburgh. Part I. Its Natural History and 
Chemistry. (Plates I.-VIL), . . . .955 

XXII. On the Foundations of the Kinetic Theory of Gases. III. By 

Professor Tait, ...... 1029 

XXIII. On Systems of Solutions of Homogeneous and Central Equations 
of the nth Degree and of two or more Variables ; with a Dis- 
cussion of the Loci of such Equations. By the Hon. Lord 
M'Laren. (Plates I. -VI.), .... 1043 



PAGE 



viii - CONTENTS. 

Appendix— 

The Council of the Society, . . ■ . 1102 

Alphabetical List of the Ordinary Fellows, . . . 1103 

List of Honorary Fellows, . . . • .1118 

List of Ordinary Fellows Elected during Session 1887-88, . 1120 

List of Ordinary Felloivs Elected during Session 1888-89, . 1122 

Laws of the Society, . . . . . .1125 

The Keith, Makdoug all- Brisbane, Neill, and Victoria Jubilee 

Prizes, ....... 1132 

Awards of the Keith, Makdoug all- Brisbane, Neill, and Victoria 

Jubilee Prizes, . . . . . .1135 

Proceedings of Statutory General Meetings, . . .1139 

List of Public Institutions and Individuals entitled to receive Copies 

of the Transactions and Proceedings, . . .1145 

Index, ........ 1151 



11 JUL 90 



2 P FEB 1889 



TRANSACTIONS 



OF TUG 



ROYAL SOCIETY OF EDINBURGH. 

VOL. XXXV. PART I.— (Nos. 1 to 7)— FOR THE SESSION 1887-88. 



CONTENTS. 



No. I. On the Number of Dust Particles in the Atmosphere. By John Aitken, Esq. 

(With a Plate), ... . 1 

II, The History of Volcanic Action during the Tertiary Period in the British Ides. 
By Archibald Geikib, LL.D., F.R.S., Director General of the Geological 
Survey of tlie United Kingdom. (With Two Maps and Fifty-three 
Woodcuts), .......... 21 

III. Mean Scottish Meteorology for tlie last Thirty-two Years. By C. Piazzi Smyth, 

late Astronomer-Royal for Scotland, and F.R.S.E., F.R.A.S., Sec. (With 
Fourteen Plates), . . . . . . . . .185 

IV. Eight Years' Observations of the New Earth Thermometers at tlie Royal Obser- 

vatory, Edinburgh, 1879-1888. By C. Piazzi Smyth, late Astronomer- 
Royal for Scotland, and F.R.S.E., F.R.A.S., &c. (With Four Plates), . 287 

V. On Neuropteris plicata, Sternberg, ami Xeuropteris rectinervis, Kidston, n. sp. 

By Robert Kmsrox, F.R.S.E., F.G.S. (With a Plate), . . . 313 

VI. On tlie Fossil Flora of tlie Staffordshire Coal Fields. By Robisut Kidston, 

F.R.S.E., F.G.S. (With a Plate), ...... 317 

VII. Experimental Researches in Mountain Building. By Henry M. Cadell, Esq. 
of Grange, B.Sc, F.R.S.E., H.M. Geological Survey of Scotland. (With 
Thirty-six Illustrations), ....... 337 



(Issued January 21, 1889). 



TBANSACTIONS. 



I. — On the Number of Dust Particles in the Atmosphere. By John Aitken, Esq. 

(With a Plate.) 

(Read 6th February 1888. 
' The gay motes that people the sunbeams. " — Milton. 

The solid matter floating in our atmosphere is every day becoming of greater and 
greater interest as we are gradually realising the important part it plays in the economy 
of nature, whether viewed as to its physical, physiological, or meteorological aspects. 
One fundamental point on which we have at present very little information of anything 
like a definite character, is as to the number of solid particles present in our atmosphere. 
We know that they are very numerous, and it seems probable that the number varies 
under different conditions of weather ; but what number of particles are really present 
under any conditions, and how the number varies, we have at present very little idea- 
In this field of research the physiologists are far in advance of the physicists, as they have 
devised means of counting the number of live germs floating in our atmosphere, and 
already we have a good deal of information as to how the number varies under different 
conditions. 

Part of our ignorance regarding the dead organic and inorganic matter floating in the 
atmosphere may no doubt be due to the apparent difficulty of an investigation of this 
kind, where many of the particles to be counted are so extremely small that they are not 
only invisible to the naked eye, but are beyond the highest powers of the microscope. 
But, though this may be the case, yet the real reason of our ignorance on this subject 
would rather appear to be, that no one has seriously set himself to the investigation of the 
subject ; the problem, though apparently one of considerable difficulty, has turned out 
to be of comparatively simple solution, when the degree of accuracy required is not very 
great. When we consider the numbers we have to deal with, and the conditions of the 
problem, perfect accuracy does not indeed seem possible. 

VOL. XXXV. PART 1 . A 



2 J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

Introduction to the Method of Counting. 

I shall here give an account of a method I have devised and developed for counting the 
number of dust particles in any sample of air ; and the figures which have been obtained 
will, it is hoped, help to give deflniteness to our ideas as to the numbers of the particles 
floating in the atmosphere, under both natural and artificial conditions. 

In approaching the solution of this problem, different ideas suggested themselves as to 
the manner of counting the particles, but they all depended on the fundamental prin- 
ciple of makiug them visible by supersaturating with vapour the air in which they were 
floating. Under these conditions, each dust particle becomes a centre of condensation, 
and what was invisible by itself becomes quite visible by its effects, as each invisible dust 
particle becomes a centre of condensation, and grows into an easily visible drop. 

The simplest method of carrying out this idea was to put inside a glass receiver the 
air to be tested along with some water, and to cause supersatu ration by reducing the 
pressure in the receiver by means of a pump. We know that under these conditions a 
foggy condensation takes place, the whole receiver becoming packed with small white par- 
ticles, so small that, though visible to the naked eye, they float in the air. Each of the 
fog particles so produced has a dust particle for a nucleus. Now, it might be possible to 
devise some means of making an estimate of the number of these fog particles, by some 
sort of microscopic measurement of the average distance between their centres. But, 
supposing we had done this, we should by no means have solved the problem. These 
fog particles do not represent all the dust particles present in the air ; only those having 
the greatest affinity for the vapour being visible, a large proportion having no vapour 
condensed on them. We might, after counting them, allow these visible particles to 
settle, and then again produce supersaturation, which would reveal some more particles. 
This process would, however, require to be repeated a great number of times before the 
last of them would become visible, and as we cannot prevent the evaporation of some of 
the drops, many of the particles would be counted twice ; altogether, the whole process 
seemed too complicated and unsatisfactory to be worth attempting. 

The most hopeful suggestion was to put into the receiver only a very small and 
measured quantity of the air to be tested, mixed with a large and known amount of per- 
fectly filtered dust-free air, so that the particles would be so far apart that on super- 
saturation being made, all of them would become centres of condensation, and thus by 
one treatment every particle would become visible and be counted. On trial, the first 
part of this plan was found to be of easy accomplishment ; by simply increasing the 
proportion of dust-free air to the dusty air, a stage was arrived at in which every particle 
was made visible by one supersaturation. 

Turning now to the method adopted of counting the drops. In experimenting on con- 
densation in supersaturated air having dust particles in it, I had noticed that when the 
1 (articles are few, the drops are large, that is, large comparatively to what they are when 
the condensation takes place in ordinary air ; so large are they, that they are easily seen 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 3 

showering down like fine rain. Now, it appeared to me that it might be possible to 
count the number of drops that fell on a given area. If this could be done, then the 
problem promised to be a simple one. All that would be necessary would be to fix a 
small stage or platform inside the receiver, at a known distance from the top, to have 
the surface of the stage ruled into squares of a known size, and then by simply counting 
the number of drops that fell on one of the little squares, it would be easy to make 
an estimate of the number of dust particles in the air tested. 

Supposing, for instance, that the platform was ruled with lines at right angles to each 
other, and at 1 mm. apart, and suppose the stage was fixed at 1 cm. from the top of the 
receiver. Then, if say one drop fell on each little square, that would give 100 drops per 
square centimetre, and, as there is only 1 cm. of air above the stage, there will be exactly 
100 particles per cubic centimetre of the air in the receiver ; and knowing the amount to 
which the air was diluted with pure air, and expanded by the pump, the calculation for 
the number of particles in the air tested is easily made. Such was the plan which seemed 
to give the greatest promise of success, if the details could be successfully carried out. 

The first thing to which attention was directed was to find the most suitable kind of 
stage or platform on which to receive the drops, and on which they could be most easily 
seen and counted. This simple problem took long to solve ; and now that the difficulties 
are overcome, and the apparatus so arranged that the drops are very easily seen, and 
quickly counted, it is difficult to see how the time has been spent. The first counting 
stage tried was a small piece of glass mirror, ruled on the back with fine lines, at right 
angles to each other, and at 1 millimetre apart. The back of the mirror was covered with 
black varnish to show the lines clearly. The stage was supported inside the receiver at 
a distance of 1 cm. from the top, and its surface was examined by means of a magnifying 
glass. The stage was illuminated by a gas flame placed at a short distance and slightly 
above it. 

This small mirror gave results which at first looked highly satisfactory, the drops being 
clearly visible on its surface with the aid of the magnifying glass. But when it came to 
counting the drops, the unfitness of the arrangement was evident; for over the most of its 
surface the drops appeared double, and the confusion produced by the reflected images 
caused its use to be abandoned at once. The next arrangement tried was a mirror made 
of very thick glass, so that the reflected image might be quite out of focus ; but the result 
was not satisfactory, as the cross lines on this stage had to be etched on the upper surface, 
and these lines caused a good deal of light to be reflected from the mirror, and prevented 
the drops being so easily seen as on the first one. The next attempt was made with 
microscope glass, on which I deposited silver in the usual way; but though the thin glass 
brought the drop and its reflected image almost together, yet it had to be abandoned, as 
all the samples of this kind of glass tried were too rough and full of specks, and only 
the most highly finished glass is suitable for the purpose. 

After this, glass mirrors were abandoned, and another arrangement tried. Instead of 
using a mirror lighted from above, the stage was now lighted from below, and a small piece 



4 J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

of thin and carefully selected glass was used instead of the mirror. The glass had fine 
lines etched on its surface. This arrangement gave very fair results, though not so satis- 
factory in some respects as the mirror, if only the double image of the latter could be got 
rid of. Attempts were therefore now directed to see if the mirror arrangement could not 
be improved. To get rid of the double reflection, a silver mirror seemed to be the best 
thing, if it could be got sufficiently perfect on its surface. My first attempts in this 
direction wen' made with silver deposited on highly polished glass plates, the silvered side 
of the glass being used. These mirrors gave highly satisfactory results, but were much 
too delicate, being easily destroyed by water. With some difficulty, I however succeeded 
in getting plates of solid silver with a surface sufficiently perfect for the purpose. 

Silver mirrors, with fine lines ruled on them at 1 millimetre apart, are now the only ones 
used, and are found to work very well, though they require considerable attention to keep 
them in working order. Before beginning work, the mirror is always polished, occasion- 
ally on a buff wheel with rouge, and finished off on a wool wheel. In polishing, care has 
to be taken that the plate is always rubbed in straight lines in one direction and along 
one set, and that always along the same set of ruled lines and across the other set, no 
cross or circular rubbings being made. The reason for this is, that, when the rubbing 
marks are all in one direction, it is possible so to arrange the direction of these rubbings 
with regard to the position of the light that the surface of the mirror will look black, and 
the drops shine out brightly on its surface. 

Over the receiver is placed a cover, blackened inside to exclude all light except what 
comes from the gas flame, and an opening is made in the top of it through which the 
stage is viewed by means of a lens. The mirror requires care in its adjustment with 
regard to the position of the light to enable the drops to be easily seen. It should 
be turned so that a diagonal to the little squares on its surface will point to the light. 
When the lighting is properly adjusted, the mirror appears black on looking through 
the lens, while the lines are distinctly but not brilliantly illuminated, and when the 
drops fall on the mirror they show as bright specks on the black surface. 

An interesting illustration of the spheroidal condition is often seen in these experiments. 
When the stage is very slightly warmer than the drops, they do not adhere to the plate, 
but roll on its surface, moving towards the lowest part. They glide over the little 
squares till they meet a boundary line into which they fall, and in which they roll down 
till quite evaporated. So little resistance do they meet with in their movement, that it 
is almost impossible to make the stage so perfectly horizontal that they will not roll one 
way or another. This rolling of the drops interferes much with the counting, but, as it 
can be easily avoided, counting should never be done while the stage is in this condition; 
because, in addition to the difficulty of counting, some of the drops evaporate before they 
can be counted. Glass plates seem to be more liable to this difficulty than the silver 
ones, probably owing to glass being a better absorber than silver of the radiant heat of the 
illuminating flame. 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 5 

Description of Apparatus. 

Having given a general outline of the method employed for counting the particles, I 
shall now describe more particularly the apparatus first used in this investigation. The 
general arrangement of the apparatus is shown in the Plate. All the apparatus is of the 
simplest kind, and can be easily obtained ready made, with the exception of the small 
stage on which the drops are counted. The different stages used in this investigation 
were ruled by myself with the aid of a simple instrument constructed for the purpose, 
but which need not be described here. In the figure A is the test receiver into which the 
air under investigation is introduced, and inside which the particles are counted. It is 
an ordinary glass flask with flat bottom, and supported in an inverted position. B is an 
air-pump connected with A by the india-rubber tube C. It may be mentioned that the 
pump B is drawn in the position shown in the sketch for the convenience of illustration. 
In the actual apparatus it is fixed horizontally a little above the level of the table, as this 
position has been found to be the most convenient for making a stroke of the pump while 
the eye is kept steadily applied to the magnifying glass. D is a cotton-wool filter con- 
nected with A by means of the pipe E. The pipes C and E pass through an india-rubber 
stopper in A, and project upwards into the receiver; C stops about the middle ; while E 
rises to near the top, and forms the support to which the counting stage is attached. 
F is a stopcock for closing the connection between the receiver A and the filter D. 

The air to be tested is introduced into the flask G. This flask is provided with an 
india-rubber stopper, through which pass the two tubes I and K. The tube I enters only 
a short distance into the flask, and is provided with the stopcock H. The upper branch 
of this stopcock communicates with the tube E by means of the movable air-tight joint 
L. The other tube K attached to the flask G passes downwards to near the bottom of 
the flask, while outside it is connected with the small glass vessel M in the manner shown, 
by means of a length of india-rubber tube. The vessel M is made large enough to hold 
a few cubic centimetres of water, and at the lower end, at the narrow part, is an engraved 
index line. Above the vessel M is supported the burette N. 

To keep the air under examination saturated with vapour, some water is put into the 
receiver A, and from time to time the receiver is inverted, and the water moved about 
inside the flask so as to wet the inner walls. To enable this to be done easily, there is 
a break in the metal tube E, just below the stopcock F, which is joined by means of a 
short length of india-rubber tube, so that when the ring which supports the receiver is 
removed, it can be turned about in any direction to bring the water inside in contact with 
all parts of the interior. 

The stage on which the drops are counted, as already explained, is made of a small 
plate of highly polished silver ; it is a little over 1 cm. square, and ruled with very fine 
lines at right angles to each other and at 1 mm. apart. The stage is supported inside 
the receiver A by means of the pipe E at exactly 1 cm. below the flat top of the receiver. 
The object of fixing the stage to the top of the entrance pipe is that the stage often gets 



«) J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

covered with a heavy deposit of dew, in which state it is quite useless, but when mounted 
in the manner shown, the dew is easily cleared away by heating the tube E, when the 
heat is carried forwards to the stage by the entering air on its passage from the filter to 
tin 1 receiver. It will be noticed that the stage is not placed centrally over the pipe E. 
This arrangement has been adopted because it has been found to keep the stage in the 
best working condition. If the stage is too hot, the drops roll away and quickly eva- 
porate ; on the other hand, if it is too cold, the surface gets wet, and counting becomes 
impossible. It has been noticed that the entering air tends to cool the stage, and it is 
found better to confine the cooling to one side of the stage, because, by this arrange- 
ment, thereis gene rally some part of it at the temperature most suitable for easy count- 
ing ; and, as only one or sometimes four little squares are required, there are always 
plenty to select from in the hundred on the stage. The stage is viewed through the 
bottom of the flask, by means of the compound magnifying glass S. A common cheap 
instrument, to be had from most opticians, has been found to be quite suitable for this 
purpose. 

The pipe C, connecting the pump with the receiver, terminates inside the receiver in an 
enlargement P, which is packed with cotton wool for a reason which will be explained 
later on. The stage is illuminated by means of the gas flame R, the light from which 
passes through the spherical flask Q, which is filled with water. This spherical lens sifts 
the heat out of the rays, and concentrates the light on the stage. T is a screen enclosing 
the receiver A, to cut off all light except what is concentrated on the stage by the lens 
Q, and it is blackened inside to check reflection. 

Suppose now the apparatus fitted up as shown in the figure, and that we wish to test a 
sample of air, the first thing to be done is to close the stopcock H, and open F. The 
pump B is now worked, and air drawn through the filter D, this is done for some time 
till the air begins tog etpurified; or most of the air may be pumped out and filtered air 
allowed to enter. After this has been done the stopcock F is closed, and a stroke of the 
pump made ; condensation then takes place inside the flask, and if the air is nearly pure, 
the drops are large and soon settle down. After they have fallen, the stopcock F is again 
opened, and filtered air allowed to enter, when it is again closed, and another stroke is 
made with the pump. This is repeated till all condensation stops in the flask. The air 
inside the receiver is now free from all dust particles. The stopcock F is then closed, the 
tube K disconnected from M, and the stopcock H withdrawn from its air-tight fitting L. 
The flask G being thus thoroughly disconnected from the apparatus, its stopper is now 
removed, it is filled with water, and carried to the place from which we wish to take a 
sample of the air to be tested. Here the water is nearly all emptied out of the flask, and 
the air enters to take its place. The stopper must now be tightly fitted in, the stopcock 
closed, and the pipe K filled with water and clamped. Returning with the flask to the 
apparatus, the stopcock H is carefully fitted into its place, the tube K connected with 
M, the lower part of M being full of water, and care taken that no air gets shut in between 
the water in the tube and the water in M. The stopcock H is now opened, and water 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 7 

allowed to pass from M into the flask, till the water in M falls to the index line. The 
air which has been displaced by this process from the flask G enters the tube E, and moves 
in the direction of the filter. One or two strokes of the pump and corresponding con- 
densations in the manner explained soon gets rid of this impure air. After all condensa- 
tion has ceased, some water, say 1 c.c, is allowed to run from the burette N into M, and 
one stroke of the pump is made, care being taken that both stopcocks were previously 
closed. The stopcock H is now opened till the water in M falls to the index line, after 
which it is closed. By this process 1 c.c. of air is displaced from the flask G and sent 
into the tube E. The stopcock F is now opened, and, as we had previously made a stroke 
of the pump, air rushes in from the filter and carries the 1 c.c. of dusty air along with it 
into the receiver. The stage is now carefully watched through the magnifying glass, and 
one stroke of the pump made, the eye being steadily fixed on a selected square on the 
stage. At once a shower of very fine rain is seen to fall, and the drops that fall on the 
selected square are counted. If the stage is too hot, the drops rapidly evaporate, and 
the attention must be confined to one square ; but in certain conditions, difficult as yet 
to maintain, the drops remain visible a considerable time, so the number on a great many 
squares can be counted, and an average quickly got ; but in most conditions of the stage 
the test must be repeated frequently before a satisfactory average can be obtained. The 
measured quantity of water must again be run into M, and its equivalent of air displaced 
from G into the tube E, and carried into the test receiver, condensation produced, the 
drops counted for say ten times, and the average taken. 

Too much dusty air must not be sent into the test receiver at one time, or the drops 
will be too close for counting ; and further, the whole of them will not be thrown down ; 
some of them will remain as dust, and will fall if a second expansion is made. Any error 
from having too many particles present need never take place, as in practice there is 
a constant check on the number admitted in the following manner : — After expansion 
has been made and the drops counted, the stopcock F is opened, and filtered air allowed 
to enter. A stroke of the pump is then made to prepare the receiver to draw in the air 
for the next test, and if, while this stroke is being made, we watch the stage, we shall see 
whether any drops fall or not. If none fall, then the amount of dusty air admitted has 
been within the correct limits ; but, if any drops appear, then too much has been used, and 
less water must be run into M for the next test. If no condensation took place after this 
stroke was made, the measured quantity of dusty air is again passed into the tube E, and 
carried into the receiver for another test. A complete check is thus kept on each test, 
ensuring that all the particles in each quantity of air tested have been thrown down. 

Let us now take an example to show the manner of estimating the number of particles 
in a sample of air by means of this apparatus. In addition to the number of drops per 
square millimetre, the quantities required to complete the estimate are, the capacity of 
the receiver A and of the pump B. In the apparatus sketched, A has a capacity of 500 
c.c, but, as there are 50 c.c. of water in it, its air capacity is reduced to 450 c.c. If 
into this pure air we introduce 1 c.c. of the air to be tested, the dusty air will be, 



8 J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

so to speak, diluted 450 times. But the air is not only diluted, it is also expanded by 
the pump, which has a capacity of 150 c.c. The dust that was in our original 1 c.c. is 
thus expanded by the two processes into 600 c.c. The number of drops per c.c. counted 
on the stage must therefore be multiplied by GOO to give the number in the 
original cubic centimetre of dusty air. Suppose that we counted one drop per square 
millimetre, then, as there is 1 cm. of air above the stage, this will give 100 drops per 
cubic centimetre in the diluted and expanded air, and this multiplied by 600 gives 
60,000 dust particles per cubic centimetre of the air tested. 

With apparatus of the proportions shown, the described method of working is suitable 
for air in the condition usually found outside, but it will not do for such air as is found in 
rooms where gas is burning — 1 c.c. of air of this kind when expanded only 600 times 
would give such a dense shower of drops that it would be impossible to count them. We 
might, of course, put in less than 1 c.c. of the air to be tested, but it is evident that 
accuracy cannot be obtained if very small quantities are used, because it is difficult to 
measure them correctly owing to variations in temperature and pressure, and also 
because of the imperfections of the apparatus. The tubes connecting the stopcock H are 
made of as small diameter, and as short as possible ; yet, it is evident that, however 
small we make them, they will always hold some air, which, by the construction of the 
apparatus, is counted in the measured air ; but owing to the smallness of the tubes this air 
will not have so much dust in it, as much of it will settle out while standing. 

A better plan for testing very dusty air is, first to fill the flask G with water, attach it 
to the apparatus, and after purifying the air in the receiver, open the stopcock H and 
disconnect K from M ; then syphon out a measured quantity of water, say 400 c.c, allow- 
ing filtered air to enter by H to take its place. The flask G is then disconnected from 
E, and 40 c.c. of water syphoned over, while its place is taken by the air we wish to test, 
which is allowed to enter by the stopcock H. The rest of the testing is made as before ; 
and the calculations are all as in the previous example, only multiplied by 10, or whatever 
the proportion was in which we mixed the dusty air with pure air in the flask G. 

Another method of working, and the one which was principally used in the pre- 
liminary work, is somewhat different, and seems to possess some advantages over the 
one described ; the apparatus, however, is much larger. In this other method the flask G 
and the filter D are removed, the rest of the apparatus remains as shown, and in place of 
the flask a gasometer is used. The gasometer employed has a capacity of 20 litres ; it is 
delicately hung, and accurately graduated, so that air can be measured in it to an accuracy 
of about yjtq litre. The gasometer is provided with a large filter 5 inches in diameter 
and 5 inches deep. The manner of working is as follows : — Back weights are put on, and 
air drawn in through the filter till the gasometer is nearly full. A measured quantity of 
the air to be tested is then added to it, and the mixture stirred by means of a metal disc 
which can be moved up and down inside the gasometer. 

When testing the outside air, it is introduced into the gasometer by means of a pipe, 
one end of which passes to the open air, while the other is attached to the gasometer. 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 9 

The outside air is drawn through the pipe for some time just before it is connected with 
the gasometer. One litre of air is drawn into the gasometer which had been previously 
nearly filled with filtered air, and filtered air is then added to complete the 20 litres, the 
whole is stirred, after which the stopcock attached to the gasometer is opened, and ^ of 
the air allowed to escape, after which the gasometer is again filled up with filtered air. The 
gasometer is now connected with the test receiver by means of the tube E, the air in the 
test receiver having been previously purified by means of a filter. The air from the 
gasometer is now made to flow through the test receiver for some time to expel the 
pure air, the stopcock is then closed, expansion made, and the drops counted. Or, 
instead of passing a great quantity of air through the receiver so as to expel all pure air 
from it, we may allow only just as much to enter as will supply the place of what was 
taken out by the one stroke of the pump when the expansion was made. These two ways 
of working, of course, give different numbers of drops per millimetre, but, when the 
calculations are made for the different conditions, the numbers are alike. 

The dusty air in the gasometer was, by the process described, first mixed with 19 times 
its volume of pure air, and then T \y was mixed with 9 times its volume ; so that the 
original air was diluted 200 times. This proportion is found to suit some states of the 
outside air ; but for air with more particles in it, such as the air of a room, the process 
has to be repeated twice or even three times, each process of emptying to ^, and filling 
with filtered air, requiring the number of drops to be multiplied by 10. The gasometer, 
however, is not always emptied to -j\j ; the density of the shower which appears when a 
trial expansion is made gives an idea of the amount of dilution required before correct 
counting can be done. It would save time with very dusty air to let out more than T 9 a 
before filling up with pure air, but it is not thought advisable to do so, as the measure- 
ments made with the lower part of the gasometer are never so accurate as those taken 
further up, owing to evaporation altering the level of the water. In some cases the air 
to be tested has been introduced by displacement, the air being contained in a large 
bottle and displaced by means of a measured quantity of water, attention being given to 
keep pressure correct. By this method of working, we can mix very small quantities of 
the dusty air, and make the test without emptying and filling the gasometer a number 
of times. 

On some Necessary Precautions. 

In developing a process of this kind, it was quite to be expected that many difficulties 
would present themselves. Most of these have now been overcome, but more than once 
the task appeared hopeless. Everything would go right for a time, then all at once it 
would break down. The number of particles counted in the successive tests of the same 
air would be fairly constant for a number of times ; it would then increase to an amount 
far exceeding the limits of the errors of observation. Now that the road is cleared and 
the principal obstructions removed, it is difficult on looking back to see where the 
obstructions were, as their cause, and the manner of avoiding them, are now so 

VOL. XXXV. PART 1. B 



10 J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

evident If it were uot for my note-book and the interval of time which has 
elapsed since the preliminary trials were made with the apparatus, — time which has 
been spent in clearing these obstructions, — one would be unconscious that they ever 
existed. As, however, these same difficulties will probably occur to any one who may 
be induced to follow this line of investigation, it is advisable that some reference be made 
to them, and the manner in which they may be avoided pointed out. 

When the different tests of the same air gave such different results, it was at first 
thought that the difference might be due to imperfect filtering. In the process described 
we take an amount of filtered air and mix it with a small amount of the dusty air we 
wish to test, and we assume that all the centres of condensation were dust particles con- 
tained in the dusty air. Now, it is very evident, that if the pure air is imperfectly 
filtered, our results will not be true, and the numbers will vary with the more or 
less perfect filtration of the air. As then the filtering of air lies at the very root of 
the matter, it was thought advisable to study this process more in detail, and determine 
whether it is possible by means of cotton wool to filter out all the dust particles, and, if 
possible, to determine the conditions under which this can be done. 

The apparatus used for studying this question was much the same as that represented 
in the Plate. The flask G was removed, and the pump and the filter connected with the 
receiver in the manner shown ; the connecting pipes, however, only entered the receiver to 
a height a little above the level of the water, so as to leave the interior of the receiver 
clear for observing any condensation that might take place. The gas flame was brought 
down to very nearly the level of the receiver, the light being allowed to pass through the 
opening in the screen U, the screen being painted black on the side next the receiver. 
By this arrangement a strong light was thrown into the receiver by means of the water 
lens, and by taking up a position with the eye a little above the level of the receiver, the 
light was not seen, while the illuminated drops were clearly observed against the black 
background. Some other little black screens were also introduced to cut off all light 
except that coming from the drops, but these need not be particularly referred to, as each 
operator will adjust them to suit himself. 

The filters consisted of cotton wool packed into glass tubes, similar to that shown at D 
in the figure, only of different lengths. The internal diameter of these tubes is 1 inch. 
A plug of wire-cloth was fitted into the bottom of each tube for the wool to rest on and 
prevent it pressing into the small exit tube. 

The filtering powers of different lengths of closely packed cotton wool were tested 
in the tubes, beginning with a length of 1 inch, and gradually increasing up to 12 
inch (30*5 cm.). There appeared no very definite method of measuring the effect of 
different lengths, as, in addition to the tightness with which the wool is packed, the 
filtering power depends on two things. First, the thickness or length of filter ; and 
second, the rate at which the air is passed through it. The following is the method 
employed for testing the filtering powers of tightly packed cotton wool, and will give 
an idea of the filtering power under different conditions : — The receiver employed has a 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 11 

capacity of 450 c.c, while the volume of the pump is 150 c.c. In making an experiment, 
one stroke of the pump is made, and after the drops inside the receiver have settled, the 
stopcock F is opened and air allowed to enter, the air passing through the filter on its 
way. It was found that with a length of 1 inch (2 "5 cm.) of wool in the filter, the 
air was very far from being freed from all its dust, as a shower always fell after expansion. 
But, if the rush of the air through the filter was checked, and it was made to pass slowly 
through, then all the dust was taken out. More and more wool was now packed into the 
tube, with the result, that when a length of 3 or 4 inches was attained the air might be 
allowed to rush unchecked through the filter, and yet be perfectly freed from all dust. 
Part of this better filtration is the result of the greater length of wool passed through by 
the air, but very much is due to the checking of the rush of air by the greater length 
of wool. When more wool was packed into the tube, no difference whatever was detected 
in its filtering power. It was, however, found that with even 12 inches of wool the 
filtration, though perfect under the conditions described, was imperfect if the air was 
made to rush through it more violently. If three strokes of the pump were made instead 
of one, before the stopcock F was opened, the rush of air was sufficiently violent to carry 
some dust through even 12 inches of tightly packed cotton wool. 

These results point clearly to the necessity of testing the filter connected with any 
apparatus, under exactly the conditions under which it will be used. When working with 
certain arrangements of apparatus, such as that shown in the Plate, where an air-pump is 
used, it does not matter how much wool we pack into the filter, the pressure employed 
is so great that the resistance of the filter does not practically interfere with the working 
of the apparatus, in which case it is advisable to have a great thickness of wool. But 
when working with the gasometer arrangement, the pressure available for drawing the air 
through the filter is very small, and a great length of wool would retard the filtering and 
waste much time. The filter for the gasometer was therefore made of very large area, to 
reduce the rate per unit of area at which the air passes through it ; and after enough of wool 
had been packed in to give perfect filtration, when used under the pressure at which it was 
to be worked, a large amount more was added to give a good factor of safety. In work- 
ing the gasometer arrangement, it has been customary to test the action of the filter every 
time the gasometer is being filled with filtered air. This is necessary not only to see 
that the filter is acting perfectly, but also to make sure that all dusty air has been washed 
out before we begin to fill with filtered air, as it is difficult to get rid of the last trace 
of dusty air in the gasometer and its connecting pipes, and this can be done only by 
washing with filtered air and testing. 

What I have here stated definitely with regard to the filtering powers of different 
lengths of cotton wool was very far from being clear while the investigation was going 
on. At that time, what has been stated seemed to be the general conclusion, but any 
thing like confidence in it was destroyed by the many exceptions. For instance, the 12- 
inch filter seemed to do its work perfectly, filtering the air from every dust particle, so 
long as the rush of air through it was limited to that produced by one stroke of the pump. 



12 J. A1TKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

lime after time the air would be perfectly free from all traces of condensation when 
expansion was made, then apparently without reason it would break down, a dense 
shower of rain would fall, and then the next time perhaps none, but only to be followed 
by failure before long. 

As we shall see, there were many causes for the failure of the filtered air to keep free 
from condensation when expansion was made. These we shall consider separately. This 
failure, of the air to keep clear, at first seemed unaccountable with so large a factor of 
safety as was given by 12 inches of cotton wool, which is four times what was found to 
be required for perfect filtration under what appeared to be the same conditions. The 
first thing that was suspected was some fault in the joints of the tubes where the metal 
or glass joined the india-rubber. When any new failure occurred this was always the 
first thing suspected. Time after time were the joints taken down, and remade with a 
solution of india-rubber, and the stopcocks cleaned, greased, and tested ; but in almost 
no instance were these found to be at fault, as india-rubber solution makes a perfect joint 
so long as it has not been severely strained. 

One explanation of the failure seemed to be that after all the filtering might not be 
perfect, that the filter only kept back the larger particles while it passed the extremely 
small ones. Sir William Thomson has concluded from certain phenomena of capillarity 
that the vapour pressure at a concave surface is less than that at a flat one ; and Professor 
Clerk Maxwell has extended this conclusion to convex surfaces, and has shown that the 
vapour pressure at a convex surface will be greater than that at a flat one, and that the 
smaller the body, that is the quicker its curvature, the higher will the vapour pressure be 
at its surface. From this we see that air which is saturated at a flat surface is not 
saturated at a convex one, and also that the smaller the body the higher will the super- 
saturation require to be to produce condensation on it. In our ignorance, it seemed from 
this just possible that the degree of supersaturation produced by the amount of expansion 
used in the experiments might just be about enough to cause condensation on these 
extremely small particles, so that in one test the degree might be exceeded, while in the 
next it might not be reached. 

These considerations pointed to the necessity of studying this point separately. 
Given a quantity of ordinary air, we have, in a previous communication, shown reasons 
for supposing that condensation begins before supersaturation is reached, owing to an 
affinity between the material of the dust particles and water vapour. When supersaturation 
is made in this air, these particles, owing to their affinity for water vapour, are the first 
to become visible by the vapour condensing on them. Suppose these are allowed to settle, 
then, when the next expansion and supersaturation is made, the probability is that the 
largest particles will take the next burden of vapour, and that the smaller ones will be 
left to be taken down by a subsequent supersaturation, till at last the smallest particles 
only are left to be brought down in a similar manner. This is theoretically what we 
might expect to happen, because the smaller the particle the higher will the vapour 
pressure be at its surface, and the higher therefore the supersaturation must be before 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 13 

condensation can take place on it ; but a high degree of supersaturation is not possible 
while the larger particles are present, and it is not till the air is freed from them that the 
higher degree of supersaturation necessary to cause condensation on the smaller ones is 
possible. 

In order to determine whether the showers observed with the high degree of super- 
saturation used in the tests were due to the presence of extremely small particles, it 
was necessary for us experimentally to determine whether the size of the particles has 
practically any influence on the degree of supersaturation required to cause them to 
become centres of condensation. 

In order to get an answer to this question, the apparatus was arranged very much as 
described for testing the filtering powers of cotton wool, that is with the test receiver A, 
connected on the one side with the air-pump, and on the other with the tube E, through 
which air could be drawn either from the filter or the gasometer. Through the india- 
rubber stopper in the receiver A was passed a third tube, to the lower end of which was 
attached a burette provided with a stopcock. The burette was fixed in an inverted 
position to the projecting end of the tube by means of a small piece of india-rubber 
tubing. The burette dipped into a very tall vessel full of water. This vessel was so 
arranged that it could be easily raised and lowered, or fixed at any desired height. The 
burette and vessel of water were used as an air-pump for producing small and known 
amounts of expansion of the air in the receiver. The ordinary air-pump could not be used 
for this purpose, as it is not suitable for making small and correctly measured amounts 
of expansion, and also because, in this experiment, the air which is taken out of the 
receiver at each expansion has to be returned to it, as no air from the outside can be 
admitted during the test. 

Supposing the apparatus arranged as described, the following is the manner adopted 
for testing the condensing powers of the different particles : — The air in the receiver and 
connecting tubes is first purified by pumping air through the filter. All connection is 
then cut off with the outside air by closing the stopcock F between the receiver and the 
filter. No stopcock is necessary on the exit tube, as the air-pump stops the passage of 
air in that direction. The burette stopcock is then opened, and the tall vessel of water is 
lowered till the water in the burette falls 2 c.c. The support under the vessel is then 
fixed at this level, after which the vessel is again raised to its original height and kept 
there till the water in the burette has recovered its original level. The burette stopcock 
is now closed, and the vessel lowered to its previous position. The apparatus being thus 
adjusted, the air to be tested is drawn into the receiver through the pipe E from the 
gasometer. After a short time, to allow any change of volume to adjust itself, the con- 
nection between the receiver and the gasometer is cut off, and the testing begun by 
opening the burette stopcock, when the water in it at once falls, and draws out 2 c.c. of 
air from the receiver. This expansion gives rise to condensation, the small fog particles 
being easily seen with the aid of a magnifying glass. After sufficient time has been 
given for the particles to settle, the tall vessel of water is raised, and the 2 c.c. of air are 



14 J. A1TKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

returned to the receiver. In a short time after, when the air is again saturated, the 
process is repeated, the tall vessel lowered, 2 c.c. of air drawn out, and a shower of fine 
particles produced in the receiver. 

Eepeating this process a number of times, it was found that on each succeeding 
expansion the denseness of the condensation became less and less. At first the particles 
were numerous, very small, and fell very slowly, then after a few expansions they decreased 
in number, while they increased in size, and fell more quickly. After a considerable 
number of expansions had been made, condensation entirely ceased, not a drop being- 
seen to fall. When this condition was attained, the tall vessel of water under the burette 
was lowered so as to cause an increased expansion. The vessel was lowered so much 
that on the burette stopcock being opened the water in it fell 5 c.c, arrangements for 
this having been previously made. When the stopcock was now opened, a dense shower 
of drops made its appearance in the receiver. An expansion of 5 c.c. thus produced 
condensation in air which had no nuclei for an expansion of 2 c.c. Continuing the test, 
the vessel of water was raised, and the 5 c.c. of air returned to the receiver, the stopcock 
shut, and again opened after a time, when another but less dense shower fell. After this 
was repeated a few times, no condensation took place with an expansion of 5 c.c. The tall 
vessel of water was then lowered still further, this time to an extent to cause the water 
in the burette to fall 10 c.c. When this was done, another shower made its appearance, 
but not nearly so dense as the first one which fell when the expansion was increased to 
5 c.c. After a very few 10 c.c. expansions, the condensation stopped. After this con- 
dition of matters was attained, an expansion of 150 c.c. was made by means of one stroke 
of the air-pump. When this was done, scarcely a drop made its appearance. 

We see from this experiment that a very slight degree of supersaturation will cause 
condensation on some of the dust particles in the air, but that the degree of supersatura- 
tion which is sufficient to cause some particles to become active centres, is yet insufficient 
to cause condensation to take place on others. An expansion of 2su produced a super- 
saturation sufficient to cause condensation on more than one half of the particles, but it 
required a higher degree of supersaturation to produce condensation on the others, many 
of them requiring the supersaturation produced by an expansion of ^ before vapour 
condensed on them. 

It may be concluded from this experiment that we have here distinct evidence that the 
condensing powers of the dust particles is affected by their size No doubt the com- 
position of the particles has an effect on the degree of supersaturation necessary to make 
even the small particles active, yet the affinity between the material of the particle and 
water vapour does not satisfactorily account for the different degrees of supersaturation 
required to make the different particles active. Though a small particle which has an 
affinity for vapour may have the same condensing power as a larger particle which has 
no affinity, yet the affinity alone does not explain the necessity for supersaturation to 
make any of them active ; this, so far as we know, can be explained only by the sizes. 

We see from this experiment that an expansion of ^ is nearly, perhaps quite sufficient 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 15 

to cause condensation to take place on even the smallest particles in the air tested ; from 
which we may conclude that the showers which unexpectedly took place from time 
to time in the experiments described, where high expansions were used, were not due to 
the presence of extremely small particles which had become active with the high degree 
of supersaturation. 

As already stated, Sir William Thomson has shown that the phenomena of capillarity 
give experimental proof that the vapour pressure at a concave surface is less than at 
a flat one. In the experiment above described, we have what is, so far as I am aware, 
the only experimental illustration of the complement to that conclusion, as it demonstrates 
that the vapour tension at a convex surface is greater than that at a flat one, and also 
that the smaller the body, that is, the quicker the curvature, the higher is the vapour 
pressure at its surface. 

In describing the apparatus last used, it was stated that the air tested was drawn from 
the gasometer. The object of this was that in making an experiment of the kind described, 
it would have been an almost endless task to throw down all the particles in ordinary 
air, by successive showers, in the manner described. The gasometer was therefore used 
for mixing a small quantity of the ordinary air of the laboratory with a large amount of 
filtered air. Working in this manner, we have samples of all the different kinds of dust 
in the air, and a comparatively few expansions are sufficient to complete the series 
necessary to throw down all the particles. 

In making experiments of this kind there is a necessary precaution we must refer to. 
The air under test is kept saturated by the wet sides of the receiver. It is, however, 
extremely difficult to keep the air from being supersaturated, because any difference in 
temperature of the different parts of the receiver will cause supersaturation where the hot 
saturated air mixes with the colder. Great care was therefore taken to keep the temper- 
ature as uniform as possible, all radiation being cut off, as it is easy to see that if there 
is any supersaturation due to difference of temperature, then a slight expansion would 
have the effect of a greater expansion, and interfere with the correctness of our results. 
In illustration of the effect of supersaturation from inequality in the temperature of 
the different parts of the receiver, the following experiment may be made : — Introduce 
into the receiver air in which there is only a very little dust. Now place the hand on 
one side of the receiver to heat it slightly, and watch the result. Inside the receiver will 
be seen a shower of condensed particles, which will keep falling so long as there is any 
dust in the air and the hot side of the receiver keeps wet. After it stops we may make 
an expansion by means of the pump, but no condensation will take place, the condensation 
produced by the mixing of the hot and cold currents having previously thrown down all 
the particles. 

Having then satisfied ourselves that a very small degree of expansion is sufficient to 
give rise to a supersaturation great enough to cause even the finest dust particles to 
become centres of condensation, we may dismiss the idea that the showers which gave 
so much trouble by their appearance from time to time with high degrees of expansion 



16 J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 

wen 1 due to the imperfect action of the filter. If they were not due to the presence of 
dust, then we are thrown back on the conclusion that they must have been cases of con- 
densation without nuclei. In a previous communication* reference has been made to 
instances of this kind, in which other substances than water are shown to condense with- 
out nuclei, and experiments are also described in which water vapour seemed to condense 
without nuclei when the supersaturation was sufficiently great. 

If those troublesome condensations, which took place when high expansions were used, 
were really cases of condensation without nuclei, then there seemed to be a way of pre- 
venting them. We know that water may be cooled far below the freezing point and yet 
it will not become ice, if no nuclei be present ; also that water may be heated far above the 
boiling point without passing into steam, if no free surface be present. We also know 
that any violent shock will upset the unstable equilibrium, and determine the formation 
of ice in the one case, and of steam in the other. Now, it is evident that in these two 
cases it is more the violence of the motion than the motion itself which determines the 
change. In both cases there must have been motion in the water due to convection 
currents while it was cooling or heating, but these slow movements were not sufficient to 
cause a break in the strained molecular condition. From this it seemed highly probable, 
that if we checked all violent movements of the air in the receiver, it would be 
possible to carry the supersaturation to a high degree without spontaneous condensation 
taking place ; and, on the other hand, we might, by means of violent movements and 
shocks, cause condensation to take place in supersaturated air though it was free from 
nuclei. 

Acting on this idea, a number of trials were made with air which had been passed 
through a long filter, and saturated. On drawing out the piston of the pump with a slow 
and steady stroke, no condensation ever took place ; whereas a quick stroke generally 
brought down a shower, and if the piston was made to strike the cover of the cylinder 
with a sharp blow, the shock invariably brought down a dense shower. These results 
point clearly to the conclusion that the condensation in the experiments took place without 
nuclei, as quick and slow strokes have no influence on the condensation when dust is 
present. It may be mentioned that the expansion was always made quick enough to 
prevent the air in the receiver absorbing so much heat as practically to interfere with 
the cooling effect of the expansion. 

Here then was the key to one of our difficulties, accounting for one cause of the 
variation in the number of particles counted in the successive tests of the same air. 
Many of the drops counted having no dust nucleus, as it would be inconvenient to 
regulate the stroke of the pump while attending to other matters, it was necessary to 
arrange the apparatus so as automatically to check failures of this kind. It has been 
found that this end can be attained by causing the air on its passage from the receiver 
to the pump to pass through a small opening, or, what is perhaps better, through a small 
cotton-wool filter. This filter is made dense enough to check the rush of air, and it also 

* Trans. Roy. Soc. Edin., vol. xxx. part 1. 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 17 

checks any shock being communicated from the pump to the air in the receiver. In the 
Plate it will be noticed that there is an enlargement P at the top of the exit tube C. 
The interior of P is packed with cotton wool, and a cover is put over all to keep off 
the showers of fine rain. This arrangement has been found to work perfectly, and it has 
in a simple manner removed one of our principal difficulties, keeping the air free from 
spontaneous condensation with even higher expansions than results from one stroke of 
the pump. 

It may be asked, Why was the use of such high degrees of expansion persisted in, 
when it was accompanied by so many difficulties ? One reason was the very existence of 
these difficulties themselves. They had to be satisfactorily explained before any con- 
fidence could be placed in the method of working. If we had confined our attention to 
lower expansions, we could not, for instance, have been certain that the finest particles 
were thrown down and all the dust counted. But another reason was that the high 
degree of expansion makes the drops much larger ; they therefore settle more quickly, 
and are more easily counted. 

Passing on to another necessary precaution. In making these tests, as has been 
already explained, it is necessary from time to time to turn the receiver upside down, and 
move it about in such a manner as to cause the water in it to come into contact 
with all parts of the interior. When using the 12-inch filter it was noticed that, after 
doing this, rainy condensation frequently took place on making the first expansion. It 
was thought this time that the failure might be due to some straining of the joints from 
the twisting of the tubes when moving the receiver, or that it might be due to the 
saturation being more perfect after the walls were newly wetted, and the air consequently 
more highly supersaturated on expansion, and therefore in a more favourable condition 
for producing condensation. This class of failures was, however, traced to the manner 
of wetting the inside of the flask, the particles being produced by the splashing of the 
water. If the wetting was roughly done, and there was much splashing, a considerable 
number of particles were manufactured, and a shower always took place on expansion. 
But if the water was quietly moved round inside the receiver, no condensation appeared. 

On another occasion copious showers made their appearance even when using every 
precaution, and the showers persisted, so that it looked as if the apparatus had broken 
down somewhere. At last the source of these particles was traced to a drop of water, 
which had got into the inlet pipe, and wet the lips of the stopcock. The air rushing 
over this wet surface, on its way to the receiver, had torn up the water into fine spray, 
which supplied active centres of condensation. A similar disturbance was also produced 
when the air was allowed to rush too quickly out of the gasometer into the receiver. The 
rush of air over the wet lip of the pipe, where it enters the gasometer, manufactured 
particles enough to give a good shower. 

There are some other precautions which require attention in working the apparatus 
but, as there are some developments of the apparatus at present under consideration, in 
which it is hoped these will be avoided, reference need not be made to tbem here. 

VOL. XXXV. PART 1. C 



18 J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 



Estimated Number of Particles in Airjrom different Sources. 

Having described the method of counting, the apparatus employed, and some of the 
precautions necessary in conducting the tests, I shall now give some of the numbers 
obtained by this method of counting. These numbers have all been taken with the use 
of the gasometer instead of the flask G shown in the Plate. Comparative tests have been 
made with the gasometer and flask arrangements, but not sufficiently extensive to give 
accurately their relative values. The numbers given by the flask method are generally 
less than with the gasometer, owing to the particles settling more quickly in the small 



flask than in the gasometer. 



Number of Dust Particles in Air. 



Source of Air. 


Number per c.c. 


Number per c. in. 


Outside (Raining), 
Outside (Fair), . 
Room, .... 
Room near ceiling, . 
Bunsen flame, . 


32,000 

130,000 

1,860,000 

5,420,000 

30,000,000 


521,000 

119,000 

30,318,000 

88,346,000 

489,000,000 



In the first column of the above table is entered the source of the air tested. In the 
second column the number of particles per cubic centimetre ; and for the benefit of those 
who prefer English measures, there are entered in the third column the numbers per 
cubic inch. 

The experiments made on the air of our atmosphere are too few as yet to enable 
us to draw any conclusions from them. But, so far as they go, they indicate that 
there is most dust in the air during dry weather, and perhaps during anticyclonic con- 
ditions, and least during wet weather, and perhaps in cyclonic areas. The first number 
entered in the table for outside air was taken on the 25th January, after a wet and 
stormy night. The next number is an average for dry days, while we had anticyclonic 
weather. It is hoped that, by more extended experiments, and by the use of the 
improved apparatus now under construction, some interesting meteorological results 
may be arrived at. 

The air in the laboratory was tested in the first case at a height of 4 feet from the 
floor, and gave the third number entered in the table. Air drawn from near the ceiling 
gave the fourth number. The reason of the greater number of particles in the room 
than that found outside was due to the particles produced by two gas flames burning 
in the room at the time. The air from the Bunsen flame was collected by means of a 
small chimney, and drawn direct into the gasometer, where it was mixed with filtered 
air. So full was this air of particles that it had to be mixed with 80,000 times its volume 
of filtered air before the particles were separated widely enough for counting. All the 
numbers in the table are far from being constant ; they are all found to vary much 



J. AITKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 19 

according to certain conditions, such as the time during which the gas has been burning 
in the room, manner of collecting air from the Bunsen flame, &c. 

Many will perhaps think that the numbers of particles as given in the table are far 
too high, and that there must be a mistake somewhere. It may be mentioned that the 
evidence in support of the correctness of our conclusions is similar to that of the chemist's, 
when he puts, say, a solution of sodium chloride into a solution of silver nitrate, and from 
the weight of precipitated silver chloride tells the amount of silver that was in the 
solution. If there had been no silver in the solution, then there would have been no 
precipitate ; and the amount of precipitate is in proportion to the quantity of silver 
present. So it is in testing for dust. If there is no dust in the air, no drops are thrown 
down, and the number of drops is determined by the number of particles present, for each 
drop has a dust nucleus. 

I have not yet entered carefully into the consideration of the exact value of the figures 
in the table. While the described method of counting the particles gives a very fair 
estimate of the number in the air when it arrives at the test receiver, and the numbers 
entered in the table are the numbers calculated from the particles counted there, no 
allowance has been made for the dust which may have settled in the gasometer and con- 
necting pipes. The probability, therefore, is that the figures are rather under than over 
estimates of the particles in the air tested. As showing the tendency the dust has to 
settle in the apparatus, it may be mentioned that about one half of the dust particles 
settled out of the air, if it is allowed to remain in the gasometer for one hour. In the 
development of the apparatus for this investigation, this is one of the points to which 
special attention has been given, and a method has been devised by which a very short 
time will be given for settling before the particles are counted. It is possible the dust 
might settle more slowly if the vessel containing it were dry, and mercury used instead 
of water for displacing it. This, however, with many other points, remains for considera- 
tion. It may be as well to note here, that the dust settles out of the air not only on 
account of its weight causing it to fall, but very much is settled out by difference of tem- 
perature at the different parts of the vessel. Wherever the air meets a surface colder 
than itself it parts with some of its dust to that surface, for a reason which has been 
explained in a previous communication. 

Most of us were quite prepared to find that whenever the dust particles in our atmo- 
sphere were counted, the figure would be a very high one ; but I imagine that the figures 
here given are such as few, if any expected, and they increase our admiration of the 
Old Testament writers' selection of dust as a type of the infinitely small and the 
innumerable. 



Trans. Roy. Soc. Edin* -Vol. XXXV 
J. AlTKEN ON THE NUMBER OF DUST PARTICLES IN THE ATMOSPHERE. 




^M 



M'Farlane & ErsVmc, Lit*h r f Edn 



; sEL 



( 21 ) 



II. — The History of Volcanic Action during the Tertiary Period in the British Isles. 
By Archibald Geikie, LL.D., F.R.S., Director General of the Geological 
Survey of the United Kingdom. (Plates I., II.) 

(Read 21st May 1888.) 



CONTENTS. 



Introduction, 

I. The Basic Dykes, .... 

§ 1. Geographical Distribution, 

2. Two Types of Protrusion, 

3. Nature of Component Bocks, 

1. External Characters, 

2. Internal Characters, 

3. Chemical Characters, 

4. Petrographical Nomenclature, 

4. Hade, 

5. Breadth, .... 

6. Interruptions of Lateral Continuity 

7. Length, 

8. Persistence of Mineral Characters, 

9. Direction, .... 

10. Termination Upwards, . 

11. Known Vertical Extension, . 

12. Branches and Veins, 

13. Connection with Intrusive Sheets 

14. Intersection of Dykes — -Repeated Dykes 

in the same Line of Fissure, 

15. Contact-Metamorphism, 

16. Relation of Dykes to Geological Structure, 

17. Data for Estimating their Geological Age, 

18. Origin and History of the Dykes, 

II. The Volcanic Plateaux, . 

1. Petrography, 

2. Areas of the Plateaux and Succession 

of Rocks in them, 

1. Antrim, . 

2. Mull, 

3. Small Isles, 

4. Skye, . . . 
§ 3. Vents of Eruption, 

a. Filled with Dolerite, &c, 

b. Filled with Agglomerate, 
4. Intrusive Sheets, 



PAGE 

21 

29 
32 
33 

35 
35 
41 
44 
45 
45 
45 
47 
48 
50 
50 
52 
55 
56 
59 

61 
62 
63 

68 

70 

74 
76 

84 

84 

89 

94 

96 

100 

101 

104 

111 



III. The Bosses and Sheets of Gabbro, 

§ 1. Petrography, 

2. Relations to the other Volcanic Rocks 

a. Skye, 

b. Rum, ..... 

c. Ardnamurchan, . 

d. Mull, 

3. Structure of the Gabbro Areas, . 

IV. The Acid Rocks, .... 

§ 1. Petrography, .... 

1. Pitchstone and Trachyte Series, 

2. Felsite, Quartz-Porphyry, Grano 

phyre, and Granite Series, 
2. Types of Structure, 

1. Bosses, 

a. Mull, . 

b. Small Isles, 

c. Skye, 
Relation of these Bosses to 

other Members of the Vol 
canic Series, 

(1) Relation to older 

Eruptive Vents. 

(2) Relation to the 

Bedded Basalts of 
the Plateaux, . 

(3) Relation to the Gab- 

bros, 

(4) Relation to the Basic 

Dykes and Veins, . 

d. St Kilda, .... 

e. Antrim, .... 

2. Sills or Sheets, . . . . 

3. Veins and Dykes, 

4. Superficial Lava Streams, . 



PAGE 

122 

122 
124 
126 
132 
137 
137 
140 

143 

145 
145 

147 
150 
151 
152 
159 
160 



164 



164 



165 
168 

169 

170 
170 
172 
175 
178 



V. Summary, 181 



Introduction. 

Among the problems for the study of which the remarkably varied geology of the 
British Isles offers peculiar facilities, perhaps none ranks higher in importance or in 
general interest than the history of volcanic action. Placed on the oceanic border of 
an ancient continental area, the region of Britain has lain within the limits where 

VOL. XXXV, PART 1. D 



22 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

liypogene activity is specially prone to manifest itself. From early geological times this 
activity has been displayed in various characteristic forms. Hence, within the geological 
records of Britain there has been preserved a more continuous and complete chronicle 
of volcanic phenomena than, so for as I am aware, has yet been discovered in any tract 
of similar size on the face of the globe. The rocks of the country have been investigated 
so long and so minutely that their general chronological succession has been accurately 
ascertained, and hence the precise horizon of each volcanic episode can be definitely fixed. 
The varying phases of eruptivity in different geological periods can be made out, and a 
large body of evidence can thus be amassed bearing on the general question of the past 
history of volcanism. 

Taking the broadest view of the subject, we find that the volcanic history of Britain 
naturally divides itself into two widely separated periods. The first of these embraces 
the vast Palaeozoic ages ; the second falls entirely within older Tertiary time. Between 
these two periods comes the prolonged interval marked by the whole series of Mesozoic 
formations in which, save at their base, in the lower Triassic rocks of Devonshire, no trace 
of contemporaneous volcanic action is known. It is to the records of the second of the 
two great volcanic eras that the present memoir is devoted. 

Before entering upon the detailed investigation, it may be useful to sketch briefly 
what has been the progress of opinion regarding the phenomena to be discussed. The 
basaltic cliffs of Antrim and the Inner Hebrides had attracted the notice of passing 
travellers, and their striking scenery had become more or less familiar to the reading 
public, before any attention was paid to their remarkable geological structure and history. 
In particular, the wonders of the Giant's Causeway and the Isle of Staffa had already 
begun to draw pilgrims, «ven from distant countries, at a time when geology was still in 
its earliest infancy. The scientific tourist of those days who might care to look at rocks, 
was, in most cases, a mineralogist, for whom their structural relations and origin were 
subjects that lay outside of the range of his knowledge or habits of thought. One of 
the earliest traces of an intelligent appreciation of some of the geological interest of the 
region is to be found in Whitehurst's Inquiry into the Original State and Formation 
of the Earth (2nd edit., 1786), where a good account of the basalt-cliffs of Antrim is 
given, and where the basaltic rocks are regarded as the results of successive outflows of 
lava from some centre now submerged beneath the Atlantic. More important are the 
observations contained in two letters of Abraham Mills, published in the Philosophical 
Transactions for 1790. This writer had been struck with the dykes on the north coast 
of Ireland, and was led to examine also those in some of the nearer Scottish islands. 
He believed them to be of truly volcanic origin, and spoke of them as veins of lava. 
A few years later, Faujas St Fond made his well-known pilgrimage to the Western Isles. 
Familiar with the volcanic rocks of the Continent, he at once recognised the volcanic origin 
of the basalts of Mull, Staffa, and the adjoining islands. His Voyage, published in Paris 
in 1797, may be taken as the beginning of the voluminous geological literature which has 
since gathered round the subject. Three years afterwards (1800) appeared Jameson's 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 23 

Outline of the Mineralogy of the Scottish Isles. Fresh from the teaching of Werner 
at Freiberg, the future distinguished Professor of Natural History in the Edinburgh 
University naturally saw everything in the peculiar Wernerian light. He gave the first 
detailed enumeration of some of the eruptive rocks of the Hebrides, but of course 
ridiculed the idea of their igneous origin. Having heard of a reported " crater of a 
volcano " near Portree, he ironically expressed a hope that " probably there may be still 
sufficient heat to revive the spirits of some forlorn fire-philosopher, as he wanders 
through this cold, bleak country." 

The advent of Jameson to Edinburgh gave a fresh impetus to the warfare of the 
Plutonists and Neptunists, for he brought to the ranks of the latter a mineralogical skill 
such as none of their Scottish opponents could boast. The igneous origin of basalt, 
which the Plutonists stoutly maintained, was as strongly denied by the other side. For 
some years one of the most telling arguments against the followers of Hutton was 
derived from the alleged occurrence of fossil shells in the basalt of the north coast of 
Ireland. Kir wan, whose Essays appeared in 1799, quoted with evident satisfaction 
Richardson's observation of " shells in the basalt of Ballycastle," and Eichardson him- 
self, though the true explanation that the supposed basalt is only Lias shale altered by 
basalt, had been given in 1802, by Playfair, in his Illustrations of the Huttonian 
Theory, continued for ten years afterwards to reiterate his belief in the aqueous origin of 
basalt. Thus the Tertiary volcanic rocks furnished effective weapons to the combatants 
on both sides. The dispute regarding the black fossiliferous rocks of Portrush had the 
effect of drawing special attention to the geology of the north of Ireland. Among the 
more noted geologists who were led to examine them, particular reference must be made 
to Conybeare and Buckland, who, in the year 1813, studied the interesting coast-sections 
of Antrim. The report of their observations gives an excellent summary of the arguments 
for the truly igneous origin of basalt, and a statement of opinion in favour of the view 
that the bedded basalts are the products of submarine volcanoes. Berger also about 
the same time described in fuller detail the geology of the Antrim district, and showed the 
rocks of the basalt-plateau to be younger than the Chalk. He likewise made a study of the 
basalt-dykes of the north of Ireland, and was the first to point out their prevalent north- 
westerly direction. These memoirs, contained in the third volume of the Transactions of 
the Geological Society, may justly be regarded, to quote the words of Portlock, as " the 
first effectual step made in Irish geology." Portlock's own Report on Londonderry, 
published in 1843, is still the most complete summary of information regarding the 
geology of that interesting region. 

While such advances were being made in the knowledge of the structure of the 
volcanic rocks of the north of Ireland, the geologist had already appeared who was the 
first to attempt a systematic examination of the Western Islands, and whose published 
descriptions are still the chief source of information regarding the geology of this 
extensive region. Dr Macculloch seems to have made his first explorations among the 
Hebrides some time previous to the year 1814, for in that year there were published, in 



24 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

the second volume of the Transactions of the Geological Society, some remarks by him 
on specimens from that district transmitted to the Society. For several years in 
succession he devoted himself with great energy and enthusiasm to the self-imposed 
task of geologically examining and mapping all the islands that lie to the westward of 
Scotland, from the remote St Kilda even as far as the Isle of Man. From time to time, 
notices of parts of his work were given in the Transactions of the Geological Society. 
But eventually in 1819 he embodied the whole in his Description of the Western 
Islands of Scotland. 

This great classic marks a notable epoch in British geology. Properly to estimate its 
value, we should try to realise what was the state of the science in this country at the 
time of its appearance. So laborious a collection of facts, and so courageous a resolution 
to avoid theorising about them, gave to his volumes an altogether unique character. 
His descriptions were at once adopted as part of the familiar literature of geology. His 
sections and sketches were reproduced in endless treatises and text- books. Few single 
works of descriptive geology have ever done so much to advance the progress of the science 
in this country. With regard to the special subject of the present memoir, Macculloch 
showed that the basalts and other eruptive rocks of the Inner Hebrides pierce and over- 
lie the Secondary strata of these islands, and must therefore be of younger date. But 
though he distinguished the three great series of " trap-rocks," " syenites " and " hyper- 
sthene-rocks " or " augite-rocks," and indicated approximately their respective areas, he did 
not attempt to unravel their relations to each other. Nor did he venture upon any 
speculations as to the probable conditions under which these rocks were produced. He 
claimed that those who might follow him would find a great deal which he had not 
described, but little that he had not examined. Subsequent observers have noted many 
important facts, of which, had he observed them, he would at once have seen the meaning, 
and which he certainly would not have passed over in silence. But as a first broad out- 
line of the subject, Macculloch's work possesses a great value, which is not lessened by 
the subsequent discovery of details that escaped his notice, and of points of geological 
structure which he failed to discover. 

It may here be remarked, that among the earliest and ablest observations of the 
volcanic rocks of this country were those made by foreigners. In some cases, students 
who had repaired from abroad to Edinburgh for education caught the geological 
enthusiasm then so marked in this city, and made numerous journeys through the 
country in search of further knowledge of its rocks and minerals. In other instances, 
geologists of established reputation, attracted by the interest which the published 
accounts of Scottish geology had excited, were led to visit the country and to record their 
impressions of its rock-structure. Of the first class of observers the two most noted were 
Ami Boue and L. A. Necker. Boue took his degree of M.D. at Edinburgh in 1816. 
During his stay in Scotland he made extensive tours across the kingdom, and acquired a 
wide knowledge of its rocks and minerals. In the year 1820 he published his Essai 
geologique sur VEcosse. The value of this work as an original contribution to the 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 25 

geology of the British Isles has probably never been adequately acknowledged. For 
this want of due recognition the author himself was no doubt in some measure to blame. 
He refers distinctly enough to various previous writers, notably to Jameson and 
Macculloch, but he modestly mingles the results of his own personal examinations with 
theirs in such a way that it is hardly possible to ascertain what portions are the outcome 
of his own original observations. Less credit has accordingly been given to him than he 
could fairly have claimed for solid additions to the subjects of which he treated. In the 
later years of his life, I had opportunities of learning personally from him how extensive 
had been his early peregrinations in Scotland, and how vivid were the recollections which, 
after the lapse of half a century, he still retained of them. Judged simply as a well-ordered 
summary of all the known facts regarding the geology of Scotland, his Essai must be 
regarded as a work of very great value. Especially important is his arrangement of the 
volcanic phenomena of Scotland, which stands far in advance of anything of the kind 
previously attempted. Under the head of the " Terrain Volcanique," he treats of the 
basaltic formations, distinguishing them as sheets {nappes, coulees) and dykes ; and of 
the felspathic or trachytic formations which he subdivides into phonolites, trachytes, 
porphyries (forming mountains and also sheets), and felspathic or trachytic dykes. In 
the details supplied under each of these sections he gives facts and deductions which 
were obviously the result of his own independent examination of the ground, and he 
likewise marshals the data accumulated by Jameson, Macculloch, and others in such a 
way as to present a comprehensive and definite picture of the volcanic phenomena of 
Scotland such as no previous writer had ventured to give. 

L. A. Neckee, as the grandson of the illustrious De Saussure, had strong claims on 
the friendly assistance of the Edinburgh School of Geology when he went thither in 1806, 
at the age of twenty, to prosecute his studies. He was equally well received by the 
Plutonists and Neptunists, and devoted much time to the exploration of the geology, not 
only of the Lowlands, but of the Highlands and the Inner Hebrides. Most of his 
observations appear to have been made in the year 1807, but it was not until fourteen 
years afterwards that he published his Voyage en Ecosse et aux lies Hebrides/''' The 
geological part of this work must be admitted to be somewhat disappointing. The 
author's caution not to commit himself to either side of the geological controversy then 
waging, makes his descriptions and explanations rather colourless. He adds little to what 
was previously known, and even as regards the true volcanic origin of the basalts of 
the Western Islands he could not make up his mind, contenting himself by referring 
them to "the trappean formation." But these islands had so fascinated him that 
eventually he returned to them as his adopted home, passed the last twenty years 
of his life among them, and died and was buried there. Besides his Voyage, he 
published in French an account of the dykes of the Island of Arran which appeared 
in vol. xiv. of the Transactions of this Society. 

* See biographical notice of L. A. Necker, by Principal J. D. Forbes, Proc. Boy. Soc. Edin., v. (1862) p. 53. 



26 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

Among the foreign geologists who have been drawn to the mountains and islands of 
Scotland by the interest of its rocks, I have already alluded to Faujas St Fond. Much 
more important, however, were the observations made some thirty years later by two 
German men of science, Von Oyenhausen and Von Dechen. Their careful descriptions 
of the geology of Skye, Eigg, and Arran added new materials to the knowledge already 
acquired by native geologists.* To some of the more interesting parts of their work, 
reference will be made in later parts of this memoir. 

The numerous trap-dykes of Northumberland, Durham, and Northern Yorkshire at an 
early date attracted the attention of geologists. As far back as 1817, they had been 
the subject of a memoir by N. J. Winch, who gave an account of their effects on the 
adjacent rocks. More important were the subsequent papers on the same subject by 
Sedgwick, who, discussing the lithological characters, probable origin, and geological age of 
the dykes, pointed out that while the Cleveland dyke was undoubtedly younger than a large 
part of the Jurassic rocks, there was no direct evidence to determine whether the dykes 
farther north were earlier or later than the time of the Magnesian Limestone. Subsequent 
accounts of the dykes of the same region were given by Buddle,! M. Forster,| N. 
Wood,§ H. T. M. Witham,|| Tate,H and others, while in more recent years important 
additions to our knowledge of these dykes and of their effects have been made by Sir J. 
Lowthian Bell** and Mr J. J. H. Teall.H" 

The geological age of the great series of Tertiary volcanic rocks has only been 
determined, district by district, and at wide intervals. That some part of the Antrim 
basalts are younger than the Chalk of that region was clearly shown by Berger, Cony- 
beare, and Buckland. Portlock, however, in his Report on Londonderry, &c, referred 
to the occurrence of detached blocks of basalt which he supposed to be immersed in the 
Chalk near Portrush, and which inclined him to believe that " the basaltic flows com- 
menced at a remote period of the Cretaceous system." Macculloch showed that the 
corresponding basaltic plateaux of the Inner Hebrides were certainly younger than the 
Oolitic rocks of that region. But no nearer approximation to their date had yet been 
made. In the year 1850 the Duke of Argyll announced the discovery of strata con- 
taining fossiliferous chalk-flints and dicotyledonous leaves, lying between the bedded 
basalts of Ardtun Head, in the Isle of Mull. J J In the following year these fossil leaves 
were described by Edward Forbes, who regarded them as decidedly Tertiary, and most 
probably Miocene. This was the first palseontological evidence for the determination of 
the geological age of any portion of the basalt-plateaux, and it indicated that the basalts 
of the south-west of Mull were of older Tertiary date. Taken also in connection with 
the occurrence of lignite-beds between the basalts of Antrim, it proved that these 
volcanic plateaux were not due to submarine eruptions, as the earlier geologists had 

* Karsten's Archiv (1829), vol. i. p. 56. t Trans. Nat. Hist. Soc Northumberland, i. (1831) p. 9. 

t Op. cit., i. p. 44. § Op. cit., i. pp. 305, 306, 308, 309. 

|| Op. cit., ii. (1838) p. 343. 1 Trans. Northumberland and Durham, ii. (1868) p. 30. 

** Proc. Roy. Soc, xxiii. (1875) p. 543. tt Quart. Jour. Geol. Soc, xl. (1884) p. 209. 

XX Hrit. Assoc Report, 1850, sections, p. 70, and Quart. Jour. Geol. Soc, vii. (1851) p. 87. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 27 

supposed, but pointed to the subserial outpouring of lava at successive intervals, during 
which terrestial vegetation sprang up upon the older outflows. 

While Forbes brought forward palseontological proofs of the Tertiary age of the 
volcanic rocks of the south-west of Mull, he at the same time laid before the Geological 
Society a paper on the Estuary Beds and the Oxford Clay of Loch Staffin, in Skye, 
wherein, while admitting the existence of appearances which might be regarded as 
favourable to the view that the intercalated basalts of that region were of much later 
date than the Oolitic strata between which they might have been intrusively injected, he 
stated his own belief that they were really contemporaneous with the associated stratified 
rocks, and thus marked an outbreak of volcanic energy at the close of the Middle Oolitic 
period.* The Duke op Argyll, in the paper which he on the same occasion communi- 
cated to the Geological Society, adopted this view of the probable age of most of the 
basalts of the Western Islands. He looked upon the Tertiary volcanic rocks of Mull as 
occupying a restricted area, the great mass of the basalt of that island, like that of Skye, 
being regarded by him as probably not later than some part of the Secondary period. 

It must be granted that the appearances of contemporaneous intercalation of the 
basalt among the Secondary strata are singularly deceptive. When, several years after 
the announcement of the Tertiary age of the basalts of Ardtun, I began my geological 
work in the Inner Hebrides, I was led to the same conclusion as Edward Forbes, and 
expressed it in an early paper, read before this Society in 1861, on the " Chronology of 
the Trap-rocks of Scotland."t All over the north of Skye I traced what appeared to be 
evidence of the contemporaneous interstratification of basalts with the Jurassic rocks, 
and I concluded (though with some reservation) that the whole of the vast basaltic 
plateaux of that island were not younger than some later part of the Jurassic period. 
In that paper the attention of geologists was called to the probable connection of the 
great system of east-and-west dykes traversing Scotland and the north of England, with 
the basalt-plateaux of the Inner Hebrides, and as I believed the latter to be probably of 
the age of the Oolitic rocks, I assigned the dykes to the same period in geological history. 
But subsequent explorations enabled me to correct the mistake into which, with other 
geologists, I had fallen regarding the age of the volcanic phenomena of the Western 
Islands. In 1867 I showed that, instead of being confined to a mere corner of Mull, the 
Tertiary basalts, with younger associated trachytic or granitic rocks, covered nearly the 
whole of that island, and that in all likelihood the long chain of basaltic masses, extend- 
ing from the north of Ireland along the west coast of Scotland to the Faroe Islands, and 
beyond these to Iceland, was all erupted during the Tertiary period. At the same time 
I drew special attention to the system of east-and-west dykes as proofs of the vigour of 
volcanic action at that period, and I furnished evidence that this action was prolonged 
through a vast interval of time, during which great subserial denudation of the older 
lavas took place before the outflow of the younger. J Later, in the same year, in 

* Quart. Jour. Geol. Soc, vol. vii. (1851) p. 104. t Trans. Boy. Soc. Edm., xxii. (1861) p. 649. 

% Proc. Boy. Soc. Edin., vi. (1867) p. 71. 



•J> DR GEIK1E ON THE HISTORY OF VOLCANIC ACTION 

an address to the Geological Section of the British Association, I reiterated these views, 
and more particularly emphasised the importance of the system of dykes, which in my 
opinion was possibly the most striking manifestation of the vigour of Tertiary volcanic 
action.* In 1871, after further explorations in the field, I gave a detailed account of 
the structure which had led to the mistake as to the age of the Tertiary volcanic rocks 
of the Western Islands ; and in a description of the island of Eigg, I brought forward 
data to show the enormous duration of the Tertiary volcanic period in the west of 
Britain. t It was my intention that the paper in which these views were enunciated 
should be continued in a subsequent series of memoirs. Before the preparation of the 
second of the series was completed, Mr J. W. Judd read before the Geological Society 
(21st January 1874) a paper " On the Ancient Volcanoes of the Highlands. "I The most 
novel feature of this paper was the announcement that the author had recognised 
the basal wrecks of five great central volcanoes in the Western Islands, among which 
that of Mull was inferred by him to have been at least 14,500 feet high. He was led 
to the conclusion that the volcanic period in these regions was divisible into three 
sections, — the first marked by the outburst of acid rocks (felspathic lavas and ashes, 
connected with deeper and more central granitic masses); the second by the extrusion 
of basic lavas and tuffs (the basaltic plateaux) ; the third by the appearance of small 
sporadic volcanic cones (" felspathic, basaltic, or intermediate in composition ") after the 
great central cones had become extinct. It will be seen from the present communication 
that the views adopted by Professor Judd are not those to which my study of the 
subject has led me. I have not been able to discover evidence of any great central 
volcanoes, and have found the order of outflow of the successive groups of rocks to have 
been the reverse of what he believed it to be. The appearance of his memoir, however, 
led me to postpone the continuation of the series of papers which I had begun. The 
conviction that, in some way or other, as yet wholly inexplicable to me, the dykes, 
which at so early a period of my researches arrested my attention, had played a leading 
part in the volcanic phenomena of the Tertiary period, became every year stronger. 
At last, in the year 1879, during a traverse of some portions of the volcanic region of 
Wyoming, Montana, and Utah, I was led to perceive the meaning of what had hitherto 
been so puzzling. Eiding over those great plains of basalt, and looking at the sections 
cut by the rivers through the thick series of horizontal basalt-beds underlying them, 
I appreciated for the first time the significance of Richthofen's views regarding 
" massive " or " fissure-eruptions," as contradistinguished from those of central volcanoes 
like Etna or Vesuvius, and I saw how completely the structure and history of these 
tracts of Western America explain those of the basalt-plateaux of Britain. § Since that 
year, at such intervals of leisure as I could command, I have renewed the investigation, 
and now at last, after a quarter of a century of more or less continuous labour in the 

* Brit. Assoc. Report (Dundee), 1867, sects, p. 49. t Quart. Jour. Geol. Soc, xxvii. (1871) p. 279. 

I Quart. Jour. Geol. Soc, xxx. (1874) p. 220. 

§ Geological Essays at Home and Abroad, pp. 271, 274; Nature, November 1880. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 29 

subject, I offer my results to the Royal Society of Edinburgh, which honoured and 
encouraged me by printing in its Transactions my first essay on the volcanic rocks of 
this country. 

In describing the geological history of a great series of rocks, chronological order is 
usually the most convenient method of treatment. Where, however, the rocks are of 
volcanic origin, and do not always precisely indicate their relative age, and where more- 
over the same kinds of rock may appear on widely separated geological horizons, it is 
not always possible or desirable to adhere to the strict order of sequence. With this 
necessary latitude, I propose to follow the chronological succession from the older to the 
newer portions of the series. I shall treat first of the system of basic dykes, by which so 
large a part of Scotland and of the north of England and Ireland is traversed. Many of 
the dykes are undoubtedly among the youngest members of the volcanic series, and in 
no case can their age be determined except relatively to the antiquity of the rocks which 
they traverse. They must, of course, be posterior to these rocks, and hence it would be 
quite logical to reserve them for discussion at the very end of the whole volcanic 
phenomena. My reason for taking them at the beginning will be apparent in the sequel. 
After the dykes, I shall describe the great volcanic plateaux which, in spite of vast 
denudation, still survive in extensive fragments in Antrim and the Inner Hebrides. The 
eruptive bosses of basic rocks that have broken through the plateaux will next be discussed. 
An account will then be given of the protrusions of acid rocks which mark the latest 
phase of eruption in the region. The last section of the memoir will contain a summary 
of the history of Tertiary volcanic action in Britain. 

I. THE BASIC DYKES. 

If a geologist were asked to select that feature in the volcanic geology of the British 
Isles which more than any other marks this region off from the rest of the European 
area, he would probably choose the remarkable system of wall-like masses of erupted 
igneous rock to which the old Saxon word " dykes" has been affixed. From the moors of 
eastern Yorkshire to the Perthshire Highlands, and from the basins of the Forth and Tay 
to the west of Donegal and the far headlands of the Hebrides, the country is ribbed across 
with these singular protrusions to such an extent that it may be regarded as a typical 
region for the study of the phenomena of dykes. That all the dykes in this wide tract 
of country are of Tertiary age, I am far from believing. Some of them are of the era of 
the Old Red Sandstone, others are undoubtedly Carboniferous, while some, though later than 
the Coal Measures, may be older than the Permian, or at least the Trias formations. As 
illustrations of these older dykes, I may refer to the remarkable series which traverses the 
Carboniferous rocks of Northumberland and Durham, and which includes the well-known 
Whin Sill. That this series belongs to a totally different and greatly more ancient period 
of extrusion was indicated many years ago by Sedgwick,* who referred to the previous 

* Trans. Cambridge Phil. Soc. (1822), vol. ii. p. 23; Wincb, Geol. Trans., iv. (1814) p. 25. 
VOL. XXXV. PART 2. E 



30 DR GEIK1E ON THE HISTORY OF VOLCANIC ACTION 

observations of Winch that these dykes, though they ascend through the Coal Measures, 
never enter the Magnesian Limestone. They differ also in direction from the younger 
dykes, their general trend being south-westerly. They are further distinguished by petro- 
graphical characters. 

But when these and all other dykes which can reasonably be referred to older 
geological periods are excluded, there remains a large majority which cannot be so 
referred, but which are connected together by various kinds of evidence into one great 
system that must be of late geological date, and can be assigned to no other than the 
Tertiary period in the volcanic history of Britain. In my original memoir, "On the 
Chronology of the Trap-rocks of Scotland," where I first drew attention to this great 
system of dykes in connection with the progress of volcanic action in the country, I 
pointed out the grounds on which it seemed to me that these rocks belonged to a com- 
paratively late geological date. My own subsequent experience and the full details of 
structure collected by my colleagues of the Geological Survey in all parts of the country, 
have amply confirmed this view, though, as already stated, instead of placing the era of 
eruption in the Jurassic, I now put it in the older part of the Tertiary period. The 
characters which link this great series of dykes together as one connected system of late 
geological date are briefly enumerated in the following list, and will be more fully discussed 
in later pages. 

1. The prevalent tendency of the dykes to take a north-westerly or westerly course. 
There are exceptions to this normal trend, especially where the dykes are small and 
locally numerous ; but it remains singularly characteristic over the whole region. 

2. The increasing abundance of the dykes as they are traced to the west coast and 
the line of the great Tertiary volcanic plateaux of Antrim and the Inner Hebrides. 

3. The rectilinear direction so characteristic of them and so different from the tortuous 
course of other groups of dykes. The exceptions to this normal feature are as a rule 
confined to the same localities where departures from the prevalent westerly trend occur. 

4. The great breadth of the larger dykes of the system and their persistence for long 
distances. This is one of their most remarkable and distinctive characters. 

5. The posteriority of the dykes to the rest of the geological structure of the regions 
which they traverse. They are not only younger than the other rocks, but younger 
than nearly all the folds and faults by which the rocks are affected. 

6. The manner in which they cut the Jurassic, Cretaceous, and older Tertiary strata 
in the districts through which they run. At the south-eastern end of the region they 
rise through the Lias and Oolite formations, in the west they intersect the Chalk and 
the Tertiary volcanic plateaux with their later eruptive bosses. 

7. Their petrographical characters, among which perhaps the most distinctive is the 
frequent appearance of the original glassy magma of the plagioclase-pyroxene- 
magnetite (olivine) rock, of which they essentially consist. This glass, or its more or less 
completely de vitrified representative, often still recognisable with the microscope among 
the individualised microlites and crystals throughout the body of a dyke, is also not 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



31 



infrequent as a black vitreous varnish-like coating on the outer walls, and occasionally 
appears in strings and veins even in the centre. 

It is the assemblage of dykes presenting these features which I propose to describe. 
Obviously, the age of each particular dyke can only be fixed relatively for itself. But 
when this remarkable community of characters is considered, and when the Tertiary age 
of at least a very large number of the dykes can be demonstrated, the inference is reason- 
able that the whole assemblage constitutes one great system, extravasated during a time 
of great volcanic disturbance, which could not have been earlier than the beginning 
of the Tertiary period. And this inference may be maintained even when we frankly 
admit that every dyke within the region is by no means claimed as belonging to the 
Tertiary series. 



'v-«< c ^ w . 




Fig. 1, — Dyke on the south-east coast of the Island of Mull. 



In spite of their number and the extraordinary volcanic activity to which they bear 
witness, the basic dykes form a much less prominent feature in the landscape than might 
have been anticipated. In the lowlands of the interior, they have for the most part been 
concealed under a cover of superficial accumulations, though in the water-courses they not 
infrequently project as hard rocky barriers across the channels, and occasionally form 
picturesque waterfalls. On the barer uplands, they protrude in lines of broken crag 
and scattered boulders, which by their decay give rise to a better soil covered by a 
greener vegetation than that of the surrounding brown moorland. Among the Highland 
hills, they are often traceable from a distance as long black ribs that project from the naked 
faces of crag and corry. Along the sea coast, their peculiarities of scenery are effectively 
displayed. Where they consist of a close-grained rock, they often rise from the beach as 



32 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

straight walls which, with a strangely artificial look, mount into the face of the cliffs on the 
one side, and project in long black reefs into the sea on the other (fig. 1). Every visitor 
to the islands of the Clyde will remember how conspicuous such features are there. But it 
is among the Inner Hebrides that this kind of scenery is to be found in greatest perfection. 
The soft dark Lias shales of the island of Pabba, for example, are ribbed across with 
scores of dykes which strike boldly out to sea. Where, on the other hand, the material 
of the dykes is coarse in grain, or is otherwise more susceptible to the disintegrating 
influences of the weather, it has rotted away and left yawning clefts behind, the 
vertical walls of which are those of the fissures up which the molten rock ascended. 
Some good instances of this kind are well known to summer visitors on the eastern shores 
of Arran. Others, on a large scale, may be seen in the interior of the same island along 
the crests of the granite ridges, and still more conspicuously on the jagged summits of 
Blath Beinn and the Cuillin Hills of Skye. 

§ 1. Geographical Distribution. 

The limits of the region within which the dykes occur cannot be very precisely 
fixed. There can be no doubt, however, that on their southern side they reach to 
the Cleveland Hills of Yorkshire and the southern borders of Lancashire, and on 
the northern side to the farther shores of the island of Lewis — a direct distance 
of 360 miles. They stretch across the basin of the North Sea, including the Isle 
of Man, and appear in the north of Ireland north of a line drawn from Dundalk Bay 
to the Bays of Sligo and Donegal. Dykes are of frequent occurrence over the north of 
England and south of Scotland, at least as far north as a line drawn from the coast of 
Kincardineshire along the southern flank of the Grampian Hills by the head of Glen 
Shee and Loch Tay to the north-western coast of Argyleshire. They abound all along 
the line of the Inner Hebrides and the adjacent coasts of the mainland from the remoter 
headlands of Skye to the shores of county Louth. They traverse also the chain of the 
Long Island in the Outer Hebrides. So far as I am aware, they are either absent or 
extremely rare in the Highlands north of the line I have indicated. But a good many 
have been found by my colleagues in the course of the Geological Survey of the northern 
lowlands of Aberdeenshire and Banffshire. The longest of these has been traced by Mr 
L. Hinxman for rather more than two miles running in a nearly east and west direction 
through the Old Red Sandstone of Strathbogie, with an average width of about 35 feet. 
Another in the same district has a width of from 45 to 90 feet, and has been followed for 
a third of a mile. But far beyond these northern examples, I have found a number of 
narrow basalt- veins traversing the Old Red flagstones of the Mainland of Orkney, which I 
have little doubt are also a prolongation of the same late series. Taking, however, only 
those western and southern districts in which the younger dykes form a notable feature in 
the geology, we find that the dyke-region embraces an area of upwards of 40,000 square 
miles — that is, a territory greater than either Scotland or Ireland, and equal to more than 
;i third of the total land-surface of the British Isles (Plate I.). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 33 

Of this extensive region the greater portion has now been mapped in detail by the 
Geological Survey. Every known dyke has been traced, and the appearances it 
presents at the surface have been recorded. We are accordingly now in possession 
of a larger body of evidence than has ever before been available for the discussion 
of this remarkable feature in the geology of the British Isles. I have made use of 
this detailed information, and besides the data accumulated in my own note-books, I have 
availed myself of those of my colleagues in the Survey, for which due acknowledgment 
is made where they are cited. 

§ 2. Two Types of Protrusion. 

The dykes are far from being equally distributed over the wide region within 
which they occur. In certain limited areas they are crowded together, a score or more 
occurring in a single square mile, while elsewhere they appear only at intervals of several 
miles. Viewed in a broad way, they may be conveniently grouped in two types, which, 
though no hard line can be drawn between them, nevertheless probably point to two more 
or less distinct phases of volcanic action. In the first, which for the sake of distinction 
we may term the Solitary type, there is either a single dyke separated from its nearest 
neighbours by miles of intervening and entirely dykeless ground, or a group of two 
or more running parallel to each other, but sometimes a mile or more apart. The rock 
of which they consist is, on the whole, less basic than in the second type ; it includes 
the andesitic varieties. It is to this type that the great dykes of the north of England 
and the south and centre of Scotland belong. The Cleveland dyke, for example, at its 
eastern end has no known dyke near it for many miles. The coal-field of Scotland is 
traversed by five main dykes, which run in a general sense parallel to each other, with 
intervals of from half a mile to nearly five miles between them. Dykes of this type 
display most conspicuously the essential characters of the dyke-structure, in particular 
the vertical marginal walls, the parallelism of their sides, their great length, and their 
persistence in the same line. 

In the second, or what for brevity may be called the Gregarious type, the dykes 
occur in great abundance within a particular district. They are on the whole 
narrower, shorter, less strikingly rectilinear, more frequently tortuous and vein-like, and, 
on the whole, more basic in composition than those of the first type. They include the 
true basalts and dolerites. Illustrative districts for dykes of this class are the islands of 
Arran, Mull, Eigg, and Skye. 

The great single or solitary dykes may be observed to increase in number, though 
very irregularly, from south to north, and also in central Scotland from east to west. 
They are specially abundant in the tract from the Firth of Clyde along a belt of country 
some thirty miles broad on either side of the Highland line, as far at least as the valley 
of the Tay. They form also a prominent feature in the islands of Jura and Islay. 
Those of the gregarious type are abundantly and characteristically displayed in the 
basin of the Firth of Clyde. Their development in Arran formed the subject of an 



34 DR GE1KIE ON THE HISTORY OF VOLCANIC ACTION 

interesting paper by Neckeu, who catalogued and described 149 of them, and estimated 
their total number in the whole island to be about 1500.* As the area of Arran is 165 
square miles, there would be, according to this computation, about nine dykes to every 
square mile. But they are far from being uniformly distributed. While appearing only 
rarely in many inland tracts, they are crowded together along the shore, particularly at 
the south end of the island, where the number in each square mile must far exceed the 
average just given. The portion of Argyleshire, between the hollow of Loch Long 
and the Firth of Clyde on the east and Loch Fyne on the west, has recently been found by 
my colleague, Mr C. T. Clough, to contain an extraordinary number of dykes (see fig. 17). 
The coast line of Renfrewshire and Ayrshire shows that the same feature is prolonged into 
the eastern side of the basin of the Clyde estuary. But immediately to the westward of 
this area the crowded dykes disappear from the basin of Loch Fyne. In Cantire their 
scarcity is as remarkable as their abundance in Cowal. Both in the north of Ireland and 
through the Inner Hebrides, dykes are singularly abundant in and around, but particularly 
beneath, the great plateaux of basalt. Their profusion in Skye was described early in 
this century by Macculloch, who called attention more especially to their extraordinary 
development in the district of Strathaird. " They nearly equal in some places," he says, 
" when collectively measured, the stratified rock through which they pass. I have 
counted six or eight in the space of fifty yards, of which the collective dimensions could 
not be less than sixty or seventy feet." He supposed that it would not be an excessive 
estimate to regard the igneous rock as amounting to one-tenth of the breadth of the 
strata which it cuts.t 

Among the districts where dykes of the gregarious type abound at a distance from 
any of the basalt-plateaux, reference should be made to the curious isolated tract of the 
central granite core of Western Donegal. In that area a considerable number of dykes 
rises through the granite, to which they are almost wholly confined. Again, far to the 
east another limited district, where dykes are crowded together, lies among the Mourne 
Mountains. These granite hills are probably to be classed with those of Arran, as 
portions of a series of granite protrusions belonging to a far more recent period than that 
to which the youngest granitic masses of the Highlands are to be assigned. 

Though the dykes may be conveniently grouped in two series or types, which on the 
whole are tolerably well marked, it is not always practicable to draw any line between 
them, or to say to which group a particular dyke should be assigned. In some districts, 
however, in which they are both developed, we can separate them without difficulty. 
In the Argyleshire region above referred to, for example, which Mr Clough has mapped, 
he finds that the abundant dykes belonging to the gregarious type run in a general N.W. 
or N.N.W. direction, and distinctly intersect the much scarcer and less basic dykes of the 
solitary type, which here run nearly E. and W. (fig. 17). Hence, besides their com- 
position, distinction in number, breadth, rectilinearity, and persistence, the two series 
demonstrably belong to distinct periods of eruption. 

* Trans. Hoy. Soc. Edin., xiv. (1840) p. 677. t Trans. Geol. Soc, iii. (1815) p. 79. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 35 

§ 3. Nature of Component Eooks. 

The Tertiary dykes of Britain include representatives of two very distinct groups of 
igneous rocks. The vast majority of them are basic compounds, belonging to the family 
of the pyroxenic lavas, which, where the percentage of silica is relatively high, are known 
as andesites, and where it is relatively low, have been variously styled basalts, dolerites, 
melaphyres, or diabases. It is to these basic dykes that the general descriptions of the 
present section exclusively refer. The second class is composed of an acid rock, either 
more or less crystalline, such as felsite, quartz-porphyry, rhyolite or trachyte ; or vitreous, 
in the form of pitchstone. These acid dykes or veins, though extremely abundant at a 
few localities, are on the whole rare. They will be described by themselves in subsequent 
pages (p. 175). 

To the field geologist, who has merely their external features to guide him, the 
ordinary Tertiary basic dykes present a striking uniformity in general petrographical 
character. They vary indeed in fineness or coarseness of texture, in the presence or 
absence of porphyritic crystals, amygdules, glassy portions, and other points of structure. 
But there is seldom any difficulty in perceiving that they are basic rocks belonging to 
one or other of the types of the basalts, dolerites, diabases, or andesites. This sameness 
of composition, traceable from Yorkshire to Skye and from Donegal to Perthshire, is 
one of the strongest arguments for referring this system of dykes to one geological period. 
At the same time, there are enough of minor variations and local peculiarities to afford 
abundant exercise for the observing faculties alike in the field and in the study, and to 
offer materials for arriving at some positive conclusions regarding the geological processes 
involved in the uprise of the dykes. 

1. External Characters. — As regards the grain of the rock, every gradation may be 
found, from a coarsely crystalline mass, in which the component minerals are distinctly 
traceable with the naked eye, to a black lustrous basalt-glass. Each dyke generally 
preserves the same character throughout its extent. As a rule, broad and long dykes are 
coarser in grain than narrow and short ones. For the most part, there runs alongside 
each side of a dyke a selvage of finer grain than the rest of the mass. This marginal strip 
varies in breadth from an inch or less up to a foot or more, and obviously owes its origin 
to the more rapid chilling of the molten rock along the walls of the fissure. It usually 
shades away imperceptibly into the larger-grained inner portion. Even with the naked 
eye, its component materials can be seen to be more finely crystalline than the rest of the 
dyke, though where dispersed porphyritic felspars occur they are usually as large in the 
marginal strip as in any other part of a dyke. 

This finer-grained external band, so distinctive of an eruptive and injected rock, is of 
great service in enabling us to trace dykes when they traverse other dykes or masses of 
igneous rock of similar characters to their own. When one dyke crosses another, that 
which has its marginal band of finer grain unbroken must obviously be the younger of 
the two. 



36 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

But in many examples in the south of Scotland, Argyleshire, and the Inner Hebrides, 
the fineness of grain of the outer band culminates in a perfect volcanic glass. Where 
this occurs, the glass is usually jet black, more rarely greenish or bluish black in tint, 
and varies in thickness from about half an inch to a mere varnish-like film on the outer 
face of the dyke, the average width being probably less than a quarter of an inch. On 
their weathered surface, these external glassy layers, generally present a pattern of rounded 
or polygonal prominences, varying up to four or five lines or even more in diameter, and 
separated by depressions or narrow ribs that remind us of the lines seen in perlitic 
structure. The transition from the glass to the crystalline part of the marginal fine- 
grained strip is usually somewhat abrupt, insomuch that on weathered faces it is often 
difficult to get good specimens, owing to the tendency of the vitreous portion to fly off 
when struck with the hammer. The glass doubtless represents the original condition of 
the rock of the dyke. It was suddenly chilled and solidified by contact with the walls 
of the fissure. Inside this external glassy coating, the molten material had time to 
assume a more or less completely crystalline condition before solidification. Not 
infrequently the glass shows spherulitic forms, visible to the naked eye, and likewise 
a more or less distinctly developed perlitic structure. These features, however, are best 
studied in thin sections of the rock with the aid of the microscope, as will be 
subsequently referred to. 

In some dykes, the glass is not confined to the edges, but runs in strings or 
broader bands along the central portions. I have found several examples of this 
peculiarity. The most remarkable of them occurs in the well-known dyke of Eskdale, 
which runs for so many miles across the southern uplands of Scotland.* This dyke 
throughout most of its course is a crystalline rock of the less basic type. At Wat 
Carrick, in Eskdale, it presents an arrangement into three parallel bands. On either side 
lies a zone about eight feet broad of the usual crystalline material. Between these two 
marginal portions there is an intercalated mass sixteen to eighteen feet broad, of a very 
compact and more or less vitreous rock. The demarcation between this central band and 
the more crystalline zones of the outside is quite sharp, and the two kinds of rock show 
a totally distinct system of jointing. There can, therefore, be little doubt that the 
glassy centre belongs to a later uprise than the outer portions, though possibly it may 
still have been included in the long process of solidification of one originally injected 
mass of molten material. 

Mr C. T. Clough, while mapping for the Geological Survey the extraordinarily 
numerous dykes in the eastern part of Argyleshire between the Firth of Clyde and 
Upper Loch Fyne, has observed six or seven examples of dykes showing glassy 
bands in their centres, with characters similar to those of the Eskdale dyke. He 
informs me, that he has found an absence of definite and regular joints in the 
central glassy band, and on the other hand, an irregular set of divisional planes by which 
the rock is traversed, and which he compares to those seen in true perlitic structure. 

* See Proc. Roy. Phys. Soc. Edin., v. (1880) p. 241. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 37 

While, as a general rule, the external portions of a dyke are closer-grained than the 
centre, rare cases occur where the middle is the most finely crystalline part. I am 
disposed to regard these cases and the glassy centres as forming in reality no true 
exceptions to the rule, that the outer portions of a dyke consolidated first, and are there- 
fore finest in texture. For the most part, each dyke appears to be due to a single uprise 
of molten matter, though considerable movements may have taken place within its mass 
before the whole stiffened into stone. But where, after more or less complete consolidation 
had taken place, the fissure opened again, or from any other cause the dyke was split along 
its centre, any lava which rose up the rent would tend to take a finer grain than the 
material of the rest of the dyke, and might even solidify as glass. 

Large scattered crystals of felspar, of an earlier consolidation than that of the minuter 
forms of the same mineral in the general ground-mass of the rock, give a porphyritic 
structure and andesitic character to many dykes. Occasionally such crystals attain a 
considerable size. Mr Clough has observed them in some of the Argyleshire dykes 
reaching a length of between three and four inches, with a thickness of two inches. Some- 
times they are distributed with tolerable uniformity through the substance of the dyke. 
But not infrequently they may be observed in more or less definite bands parallel with 
the boundary walls. Unlike the younger lath-shaped and much smaller felspars of the 
ground-mass, they show no diminution either in size or abundance towards the edge of the 
dyke. On. the contrary, they are often conspicuous in the close-grained marginal strip, 
and they may be found even in the glassy selvage, and touching the very wall of the 
fissure. Indeed, they are sometimes more abundant in the outer than in the inner 
portions of a dyke. 

Mr Clough has given me the details of an interesting case of this kind observed by 
him in Glen Tarsan, Eastern Argyleshire : — " For an inch or so from the edge of this 
dyke," he remarks, " porphyritic felspars giving squarish sections, and ranging up to one- 
third of an inch in length, are so abundant as nearly to equal in bulk the surrounding 
ground-mass. For the next inch and a half, they are decidedly fewer, occupying perhaps 
hardly an eighth of the area exposed. Then for a breadth of three inches they come in 
again nearly as abundantly as at the sides ; after which they diminish through a band 
27 inches broad, where they may form from -^ to ^ of the rock." He found another 
case where, in a dyke several yards wide, porphyritic felspars, sometimes an inch long, 
are common along the eastern margin of the dyke in a band about two inches broad, 
but are nearly absent from the rest of the rock. Elsewhere the crystals are grouped 
rather in patches than in bands. 

Not only are these porphyritic felspars apt to occur in bands parallel with the outer 
margins of the dykes, but they tend to range themselves with their longer axis in the 
same direction, thus even on a large scale, visible at some distance, showing the flow- 
structure, which is so often erroneously regarded as essentially a microscopic arrange- 
ment. 

Another macroscopic character of the material composing the dykes is the frequent 

VOL. XXXV. PART 2. F 



38 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 




Fig. 2.— Arrangement of lines of Amygdules 
in a Dyke, Strathmore, Skye. 



presence of amygdules. It has sometimes been supposed that the amygdaloidal structure 
may be relied upon as a test to distinguish a mass of molten rock which has reached the 
surface, from one which has consolidated under considerable pressure below ground. 
That this supposition, however, is erroneous, is demonstrated by hundreds of dykes in the 
great system which I am now describing. But the amygdules of a dyke offer certain 
peculiarities which serve in a general way to mark them off from those of an outflowing 
lava. They are usually smaller, and more uniform in size, than in the latter rock. They 
are also more regularly spherical and less frequently elongated in the direction of flow. 
Moreover, they arc not usually distributed through the whole breadth of a dyke, but 

tend to arrange themselves in lines especially 
towards its centre (fig. 2). In these central 
bands the cavities are largest and depart farthest 
from the regular spherical form, so that for short 
spaces they may equal in bulk the mass of en- 
closing rock. In some rare instances, a whole 
dyke is composed of cellular basalt, like one of 
the sheets in the plateaux, as may be seen on 
the north flank of Beinn Suardal, Skye. 

Besides the common arrangement of fine- 
grained edges and a more coarsely crystalline 
centre, instances are found where one of the 
contrasted portions of a dyke traverses the other in the form of veins. Of these, I think, 
there are two distinct kinds, probably originating in entirely different conditions. In 
the first place, they may be of coarser grain than the rest of the rock; but such a 
structure appears to be of extremely rare occurrence. I have noticed some examples 
on the coast of Renfrewshire, where strings of a more coarsely crystalline texture 
traverse the finer-grained body of the rock. Veins of this kind are probably of the 
same nature as the segregation- veins, to be afterwards referred to as a frequent 
occurrence among the thicker intrusive sheets. They consist of the same minerals 
as the rest of the rock, but in a different and more developed crystalline arrangement, 
and they contain no glassy or devitrified material, except such portions of that of 
the surrounding ground-mass as may have been caught between their crystalline 
constituents. 

The second kind of veins, which though not common, is of much more frequent occur- 
rence than the first, is more particularly to be met with among the broader dykes, and 
is distinguished by a remarkable fineness of grain, sometimes approaching the texture of 
felsite or jasper, and occasionally taking the form of actual glass. Such veins vary from 
half an inch or less, up to four or five inches in breadth. They run sometimes parallel 
with the walls of the dyke, but often irregularly in all directions, and for the most part 
avoid the marginal portions, though now and then coming up to the edge. They never 
extend beyond the body of the dyke itself into the surrounding rock. Though they have 



DURING THE TERTIARY PEEIOD IN THE BRITISH ISLES. 39 

obviously been injected after the solidification of the rock which they traverse, they may 
quite possibly be extrusions of a deeper unconsolidated portion of the same rock into 
rents of the already stiffened overlying parts. The field-geologist cannot fail to be 
struck with the much greater hardness of these fine-grained veins and strings that 
ramify through the coarsely crystalline dolerite, andesite, or other variety of the broader 
dykes. He can readily perceive in many cases their more siliceous composition, and the 
inferences he deduces from the rough observations he can make in the field are confirmed 
by the results of chemical analysis (see p. 44). 

In connection with veins of finer material, that may belong to a late stage of the con- 
solidation of the general body of a dyke, reference may be made here to the occasional 
occurrence of patches of an exceedingly compact or homogeneous texture immersed in 
the usual finely crystalline marginal material. They look like angular and subangular 
portions of the more rapidly cooled outer edge, which have been broken off and carried 
upward by the still moving mass in the fissure.* 

In general, each dyke is composed of one kind of rock, and retains its chemical and 
mineralogical characters with singular persistence. The difference of texture between 
the fine-grained chilled margin, with its occasional glassy coating, and the more coarsely 
crystalline centre is obviously due to the effects of different rates of cooling in what was 
no doubt originally one uniform molten mass. The glassy central bands, too, though 
they seem to indicate a rupture of the dyke up the middle, may at the same time quite 
conceivably be, as I have jsaid, extrusions from a lower portion of the dyke before the final 
solidification of the whole. The ramifying veins of finer grain that now and then traverse 
one of the large dykes are likewise explicable as parts of the same stage towards entire 
consolidation. All these vitreous portions, whether still remaining as glass or having 
undergone devitrification, are more acid than the surrounding crystalline parts of the rock. 
They represent the siliceous " mother-liquor," so to speak, which was left after the 
separation from it of the crystallised minerals, and which, perhaps entangled here and 
there in vesicles of the slowly cooling and consolidating rock, was ready to be forced up 
into cracks of the overlying mass during any renewal of terrestrial disturbance. 

But examples occur where a dyke, instead of consisting of one rock, is made up of two 
or more bands of rock which, even if they resemble each other closely, can be shown to be 
the results of separate eruptions. These, which are obviously not exceptions to the 
general rule of the homogeneity of dykes, I will consider in a later section of this paper. 

Among the petrographical varieties observable in the field is the occasional 
envelopment of portions of the surrounding rocks in the body of a dyke. Angular 
fragments torn off from the fissure-walls have been carried upwards in the ascending lava, 
and now T appear more or less metamorphosed, the amount of alteration seeming to depend 
chiefly upon the susceptibility of the enclosed rock to change from the effects of heat. 
Cases of such entanglement of foreign substances, however, are of less common occurrence 
than might have been expected. Occasionally, where the enclosed fragments are oblong, 

* See J. J. H. Teall, Quart. Jour. Geol. Soc, xl. (1884) p. 214. 



40 



DR GEIKIE ON THE HISTORY OE VOLCANIC ACTION 



they are arranged with their longer axes parallel to the walls of the dyke, showing 
flow-structure on a large scale. Mr Clough has lately found some dykes near Dunoon 
which enclose fragments of schist nearly three feet in length. 

One of the most interesting of the macroscropic features of the dykes, is the joints by 
which they are traversed. These divisional planes are no doubt to be regarded as con- 
sequences of the contraction of the original molten rock during cooling and consolidation 
between its fissure-walls. They are of considerable interest and importance, inasmuch as 
they furnish a ready means of tracing a dyke when it runs through rock of the same 
nature as itself, and also help to throw some light on the stages in the consolidation of the 
material of the dyke. 

Two distinct systems of joints are recognisable (fig. 3). Though sometimes combined 
in the same dyke, they are most conspicuously displayed when each occurs, as it 

generally does, by itself. The first and less 
frequent system of joints (a) has been deter- 
mined by lines of retreat, which are parallel to 
the walls of the dyke. The joints are then 
closest together at the margin, and may be few 
or altogether absent in the centre. They are 
sometimes so numerous, parallel and defined 
towards the borders of the dyke, as to split the 
rock up into thin flags. Where transverse joints 
are also present, these flags are divided into 





a b 

Fig. 3. — Systems of Joints in the Basic Dykes. 
a, parallel ; b, transverse. 



irregular tesserce. 



In the second or transverse system of joints (b), which is the more usual, the divisional 
lines pass across the breadth of the dyke, either completely from side to side or from one 
\v T all for a longer or shorter distance towards the other. Where this series of joints is 
most completely developed the dyke appears to be built up of prisms piled horizontally, 
or nearly so, one above another. These prisms, in rare instances, are as regular as the 
columns of a basalt-sheet. Usually, however, they have irregularly defined faces, and merge 
into each other. Where the prismatic structure is not displayed, the joints starting sharply 
at the wall of the dyke strike inwards in irregular curving lines. It is such transverse 
joints that enable the eye, even from a distance, to distinguish readily the course of a dyke up 
the face of a cliff of basalt-beds, for they belong to the dyke itself, are often at right angles 
to those of the adjacent basalt, and by their alternate projecting and re-entering angles 
are banded across with parallel bars of light and shade. Where they traverse not only 
the general mass of a dyke, but also the " contemporaneous veins" which cross it, it may 
be plausibly inferred that these veins were injected before the final solidification and 
contraction of the whole dyke. 

One of the most remarkable exhibitions of joint-structure hitherto noticed among 
these dykes, is that which occurs in the central vitreous band of the Eskdale dyke 
already referred to. The rock is divided into nearly horizontal prisms, each of which 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



41 



consists of a central more vitreous core and an outer more lithoid sheath. By the 
coherence of their polygonal and irregular faces, and the greater durability of their 
material, these sheaths project on the weathered wall of the vitreous centre of the dyke 
in a curiously reticulated grouping of prominent ribs each about two inches broad (fig. 4), 
while the vitreous cores, being more readily acted on by the weather, are hollowed out 
into little cup-shaped depressions. Each rib is thus composed of the sheaths or outer 
lithoid portions of two prisms, the line of separation being marked by a suture along the 
centre (fig. 4, b). Between this median suture and the inner glassy core the rib is further 
cut into small segments by a set of close joints, which are placed generally at right angles 
to the course of the rib (fig. 4, c). Examined with a lens, the lithoid substance of these 
sheaths has a dull finely granular aspect, like that of felsitic rocks, with scattered felspars. 
It is obviously a more devitrified condition of the material which forms the core of each 
prism. This material presents on a fresh fracture a deep iron-black colour, dull resinous 






a. b. c. 

Fig. 4. — Joint-Structures in the central vitreous portion of the Eskdale Dyke (B. N. Peach). 

a. View of a square yard of the outer wall of the vitreous central band, showing the polygonal arrangement of the prisms and 
their investing sheath of ribs. 

b. View of a smaller portion of the same wall to show the detailed structure of the ribs (a, a) and their vitreous cores (b, b). 

c. Profile of a part of the weathered face of the wall, showing the way in which the hard ribs or sheaths project at the surface. 



lustre, and vitreous texture. It at once recalls the aspect of many pitchstones, and in the 
early days of petrography was naturally mistaken for that rock. Through its substance 
numerous kernels of more glassy lustre are dispersed, each of which usually contains one or 
more amygdules of dull white chalcedony, but sometimes only an empty black cavity. 
These black glistening kernels of glass, of all sizes up to that of a small bean, scattered 
through the dull resinous matrix, form with the white amygdules the most prominent 
feature in the cores ; but crystals of felspars may also be observed. Some details of the 
microscopic characters of this remarkable structure will be given in a subsequent page. 
The relation of the cores and sheaths to the prismatic jointing of the rock seems to show 
that devitrification had not been completed when these joints were established, and that 
it proceeded from the faces of each prism inwards. 

2. Internal Characters. — Much information has in recent years been obtained regarding 
the microscopic structure of some of the basic dykes. The crystalline characters of those 



42 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

in the north of England have been studied by Mr Teall,* and some of those from 
the west of Scotland have been investigated by Professor Judd and Mr Cole.1' Taken 
as a whole, the rocks composing the dykes are found, when examined microscopically, 
to consist essentially of mixtures of a plagioclase felspar, pyroxene, an iron oxide, and 
sometimes olivine, usually with more or less interstitial matter. 

The felspar appears to be in some cases labradorite, in others anorthite, but there 
may be a mingling of several species in many of the dykes, as in the augite-andesite of 
the Santorin eruption in 1866, wherein Fouqtje found the larger porphyritic felspars 
were mainly labradorite, but included also anorthite, while those of the ground-mass 
were microliths of albite and oligoclase4 The large felspars scattered porphyritically 
through the ground-mass are evidently the result of an early consolidation. They 
are often cracked, and penetrated by the ground-mass, or even broken into fragments. 
They also include portions of the ground-mass, and present the zonal growth 
structure in great perfection. The small felspars of the ground-mass, on the other 
hand, are as obviously the result of a later crystallisation, for they vary in size and 
crystallographic development according to their position in the dyke. Those from the 
centre are often in well-formed crystals, which sometimes pass round their borders into 
acicular microliths. Those in the marginal parts of the dyke occur chiefly in the form 
of these microliths. Curious skeleton forms, composed of aggregates of microliths, 
connect the latter with the more completely developed crystals, and illustrate the mode of 
crystallisation of the felspathic constituents of the dykes. § 

The pyroxene is probably in most cases monoclinic (black or common augite), but is 
sometimes rhombic (usually enstatite, less frequently perhaps hypersthene). It occurs 
in (a) well-developed crystals, (b) crystalline masses with some of the faces of the crystals 
developed, (c) granular aggregates which polarise in one plane, (d) separate granules and 
microscopic microliths, which may be spherical (globulites) or oblong (longulites). 

The black iron oxide is sometimes magnetite, sometimes ilmenite, or other titaniferous 
ore. Apatite not infrequently occurs among the original constituents. Olivine is 
entirely absent from many of the dykes, and no serpentinous matter remains to indicate 
that it was ever present in them. But it is also to be met with in numerous cases, either 
in sparsely scattered or in tolerably abundant crystals. Biotite occasionally appears. 
Among the secondary products, calcite and pyrites are doubtless the most common. To 
these must be added quartz, chalcedony, and various zeolitic substances, besides the 
" viridite " and " opacite," which result from the decomposition of the ferro-magnesian 
constituents and the oxidation of the ferrous oxides. 

In many dykes there is little or no interstitial matter between the crystalline 
constituents of the ground-mass. In others this matter amounts to a half or more of 
the whole composition, and from such cases we may trace a series of gradations until 

* Quart. Jour. Geol. Soc, vol. xl. (1884). 

t Op. cit., vol. xxxix. (1883) p. 444 (basalt-glass) ; xlii. (1886) p. 49, where Professor Judd discusses the gabbros, 
dolerites, and basalts as a whole. See postea, p. 77, note. % Santorin et ses Eruptions, 1879 p. 203. 

§ See Mr Teall's excellent description of the Cleveland dyke, in the paper above cited. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



43 




we arrive at a complete glass containing only the rudimentary forms of crystals 
(globulites, longulites, &c), with scattered porphyrinic crystals of an earlier consolida- 
tion. The process of the disappearance of this original glass may be admirably studied 
in many dykes. At the outer wall, the glass remains nearly as it was when contact with 
the cold walls of the fissure solidified it. From that external vitreous layer the 
successive devitrification products and crystalline growths may be followed inwards 
until in the central parts of the dyke little trace of the interstitial matter may 
be left. 

The most instructive example of the process of devitrification which has come under 
my observation occurs in the Eskdale dyke. The central " cores " already referred to 
present a true glass, which in thin sections is perfectly 
transparent and almost colourless, but by streaks and 
curving lines of darker tint shows beautiful flow-structure. 
The devitrification of this glass has been accomplished by 
the development of crystallites and crystals, which increase 
in number until all the vitreous part of the rock disappears. 
What appears under a low power to be a structureless or 
slightly dusty glass can be resolved with a higher objective 
into an aggregate of minute globules or granules (globulites), 
which average perhaps -^o.Vou °f an mcn m diameter. 
Some of these bodies are elongated and even dichotomous 
at the ends. These granules are especially crowded upon 
clear yellow dart-shaped rods, which in turn are especially 
prominent upon crystals and crystalline grains of augite 
which bristle with them, while the immediately surround- 
ing glass has become clear. There can be little doubt 
that these rudimentary bodies are stages in the arrested 
development of augite crystals. There occur also opaque 
grains, rods, and trichites, which no doubt consist in whole 
of magnetite (or other iron oxide), or are crusted over with that mineral. 

At least two broad types of microscopic structure may be recognised among the basic 
dykes, (l) Holocrystalline, or with only a trifling proportion of interstitial matter. 
This type includes the dolerites and basalts, as well as rocks which German 
petrographers would class as diabases or diabase-porphyrites. The rocks are very 
generally characterised by what is known as the ophitic structure, where the lath-shaped 
felspars penetrate the augite, and are therefore of an earlier consolidation. In such cases 
there is a general absence of any true interstitial matter. The rocks of this type are often 
rich in olivine, and appear to be on the whole considerably more basic than those of the 
second group. It is observable that they increase in numbers from the centre of Scotland 
westwards, and throughout the region of the basalt-plateaux they form the prevailing 

* Proc. Roy. Phys. Soc. Edin., v. (1880) p. 255. 



Fig. 5. — Microscopic Structure of the 
vitreous part of the Eskdale Dyke. 
This section shows a crystal of augite, 
enclosing magnetite and surrounded 
with microliths, each of which consists 
of a central pale yellow rod crusted 
with pale yellow isotropic globulites. 
The glass around this aggregation is 
clear, but at a little distance globulites 
(many of them elongated and dicho- 
tomous) abound, with here and there 
scattered microliths, some of which are 
curved and spiral. (800 diameters. )* 



44 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

type. (2) In this type there is a marked proportion of interstitial substance, which is 
inserted in wedge-shaped portions among the crystallised constituents (" intersertal 
structure " of Rosenbusch). The ophitic structure appears to be absent, and olivine is 
either extremely rare or does not occur at all. The rocks of this group are obviously less 
basic than those of the other. They form the large dykes that rise so conspicuously 
through the south of Scotland and north of England, and their general characters are well 
described by Mr Teall in the paper already cited. In some instances they enclose 
abundant porphyritic felspars of earlier consolidation, and then present most of the 
characters of andesites. Professor Rosenbusch has recently extended the name of 
'■' Tholeiites" to rocks of this group in the north of England.* The vitreous condition is 
found in both types, but is perhaps more frequent in the second. The glass of the 
basalts, however, even in thin slices, is characteristically opaque from its crowded 
inclusions ; while that of the andesitic forms, though black in hand specimens, appears 
perfectly transparent and sometimes even colourless in thin slices. 

3. Gliemical Characters. — The only one of these to which reference will be made here 
is the varying proportion of silica. While the dykes as a whole are basic, some of them 
contain so high a percentage of silica as to link them with the acid rocks. The pro- 
portion of this ingredient ranges from less than 50 to nearly 60 per cent. The rocks 
with the lower percentage of acid are richer in the heavy bases, and have a specific 
gravity which sometimes rises above 3*0. They include the true dolerites and basalts. 
Those, on the other hand, with the higher ratio of silica, are poorer in the heavy bases, 
and have a specific gravity from 276 to 2*96. They comprise the "tholeiites," 
"" andesites," and other more coarsely crystalline rocks of the great eastern and south- 
eastern dykes.t 

Not only do the dykes differ considerably from each other in their relative proportions 
•of silica, but even the same dyke may be found to present a similar diversity in different 
parts of its mass. It has long been a familiar fact that the glassy parts of such basic rocks 
are more acid than the surrounding crystalline portions. The original magma may be 
regarded as a natural glass or fused silicate, in which all the elements of the rock were 
dissolved, and which necessarily became more acid as the various basic minerals crystal- 
lised out of it. J In the Eskdale dyke the silica percentage of this glassy portion is 58*67, 
that of the little kernels of black glass dispersed through the rock as much as 65'49.§ 
In the Dunoon dyke observed by Mr Clough the siliceous or jaspideous veins contain no 
less than 68 "05 per cent, of silica, while the mass of the dyke itself shows on analysis 
only 47*36 per cent.|| 

* Mikroskopische Physiographic, 2nd edition, 504 et seq. 

t For analyses of dykes, see I. L. Bell, Proc. Roy. Soc, xxiii. p. 546 ; J. S. Grant Wilson, Proc. Roy. Phys. Soc. 
Edin., v. p. 253 ; Teall, Quart. Jour. Geol. Soc, xl. p. 209 ; Judd and Cole, Quart. Jour. Geol. Soc, xxxix. p. 444. 

X On this subject see a paper by Dr A. Lagorio, " Uber die Natur der Glasbasis sowie der Krystallisationsvorgange 
im eruptiven Magma," Tschermak's Mineralog. Mittheil., viii. (1887) p. 421. 

§ J. S. Grant Wilson, Proc. Roy. Soc Phys. Edin., v. (1880) p. 253. 

|| Unpublished analyses made by Prof. Dittm.vr of Glasgow, and communicated to me by Mr Clough. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 45 

4. Petrographical Nomenclature. — It is obvious that no one term will suffice to 
describe a series of rocks presenting such, variety of mineralogical and chemical composi- 
tion as those that form the system of dykes now under discussion. Basalt, dolerite, 
melaphyre, diabase, augite-porphyrite, diabase-porphyrite, augite-andesite, and doubtless 
other names might be appropriately applied to different dykes ; sometimes, indeed, 
more than one of these terms might be given to different parts of the same dyke. When 
the geological history of the dykes, and their connection with the rest of the volcanic 
phenomena are the subject of inquiry, rather than their petrographical characters, it 
becomes convenient to adopt some general term which may appropriately describe the 
whole. The word " basalt " has been so employed, but it is obviously so inapplicable to 
the more acid and andesitic rocks that its use as a general epithet is objectionable. None 
of the other specific names are free from the same defect. The old term " trap " would be 
useful, but it has become obsolete, and its revival might be attended with grave dis- 
advantages. In referring to the dykes of this great system, therefore, I shall speak of 
them as "the basic dykes," reserving specific names for such individual cases as may 
require them. 

§ 4. Hade. 

In the great majority of cases the dykes are nearly or quite vertical. This position 
is more particularly exhibited by the great single dykes. But occasionally, where one 
of these crosses a deep valley, a slight hade is perceptible by the deviation of the 
line of the dyke from its normal course. Sedgwick long ago noticed that the 
Cleveland dyke has, in places, an inclination of at least 80° to its N.E. side.* In 
the coal-workings, also, a trifling inclination is sometimes perceptible, especially where a 
dyke has found its way along a previously existing line of fault, as in several examples 
in Stirlingshire. But in those districts where the dykes are gregarious, departures from 
the vertical position are not infrequent, more particularly near the great basalt-plateaux. 
It was long ago noticed by Necker, that even in such a dyke-filled region as Arran, almost 
all of the dykes are vertical, though sometimes deviating from that position to the extent 
of 20°.t Berger found that the angle of deviation among those of the north of Ireland 
ranges from 9° to 20°, with a mean of 13°. J The most oblique examples are probably 
those which occur in the basalt-plateaux of the Inner Hebrides, where the same dyke in 
some parts of its course runs horizontally between two beds, across which it also ascends 
vertically (see fig. 41). But with these minor exceptions, the verticality of the great 
system of dykes, pointing to the perpendicular fissure-walls between which the molten 
rock ascended, is one of the most notable features in their geological structure. 

§ 5. Breadth. 

An obvious characteristic of most dykes is the apparent uniformity of their breadth, 
Many of them, as exposed along shore-sections, vary as little in dimensions as well- 

* Cambridge Phil. Trans., ii. p. 28. t Trans. Roy. Soc. Edin., xiv. p. 677. t Trans. Geol. Soc, iii. p. 227. 

VOL. XXXV. PART 2. G 



46 DR GE1K1E ON THE HISTORY OF VOLCANIC ACTION 

built walls of masonry do. Departures from such uniformity may often indeed b« 
noted, whether a dyke is followed laterally or vertically. The largest amount of varia- 
tion is, of course, to be found among the dykes of the gregarious type, the thinner 
examples of which may diminish to a width of only one inch or less, while their average 
breadth is greatly less than in the case of the great solitary dykes. In the district of 
Strathaird, in Skye, Macculloch estimated the remarkably abundant dykes there 
developed to vary from 5 to 20 feet in breadth, but with an average breadth of not more 
than 10 feet.* In the isle of Arran, according to Necker's careful measurements, 
most of the dykes range from 2 or 3 to 10 or 15 feet, but some diminish to a few 
inches, while others reach a width of 20, 30 or even 50 feet.t In the north of Ireland, 
Berger observed that the average breadth of thirty-eight dykes traversing primitive 
rocks (schist, granites, &c.) was 9 feet; and of twenty- four in Secondary rocks, 24 feet.J 

But when we pass to the great solitary dykes, that run so far and so continuously 
across the country, we encounter much thicker masses of igneous rock. Most of the 
measurements of these dykes have been made at the surface, and the variations noted in 
their breadth occur along their horizontal extension. The Cleveland dyke, which is the 
longest in Britain, varies from 15 to more than 100 feet, with perhaps an average width 
of between 70 and 90 feet.§ Some of the great dykes that cross Scotland are of larger 
dimensions. Most of them, however, like that of Cleveland, are liable to considerable 
variations in breadth when followed along their length. The dyke which runs from the 
eastern coast across the Cheviot Hills and Teviotdale to the head of the Ale Water, is in 
some places only 10 feet broad, but at its widest parts is probably about 100 feet. The 
Eskdale and Moffat dyke is in parts of its course 180 feet wide, but elsewhere it 
diminishes to not more than 40 feet. These variations are repeated at irregular intervals, 
so that the dyke alternately widens and contracts as we trace its course across the hills. 
Some of the dykes further to the north and west attain yet more gigantic proportions. 
That which crosses Cantyre opposite Ardlamont Point has been measured by Mr J. B. 
Hill of the Geological Survey, who finds it to be from 150 to 180 feet broad on the shore 
of Loch Fyne, and to swell out beyond the west side of Loch Tarbert to a breadth of 
240 to 270 feet. A dyke near Strathmiglo, in Fife, is about 400 feet wide. The broadest 
dyke known to me is one which I traced near Beith, in Ayrshire, traversing the Carboni- 
ferous Limestone. Its maximum width is 640 feet. 

Unfortunately, it is much less easy to get evidence of the width of dykes at different 
levels in their vertical extension. Yet this is obviously an important point in the 
theoretical discussion of their origin. Two means are available of obtaining information 
on the subject — (a) from mining operations, and (6) from observations at precipices 
and between hill-crests and valley-bottoms. 

* Trans. Geol. Soc, iii. p. 80. t Trans. Roy. Soc. Edin., xiv. p. 690 et seq. 

X Trans. Geol. Soc, iii. p. 226. He believed that dykes in Secondary rocks reach a much greater thickness than in 
other formations. My own observations do not confirm this generalisation. 

§ At Cockfield, where it has long been quarried, it varies from 15 to 66 feet ; at Armathwaite, in the vale of the 
Eden, it is about 54 feet (J. J. H. Teall, Quart. Jour. Geol. Soc, xl. p. 211). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 47 

(a) In the central Scottish coal-field and in that of Ayrshire some large dykes have 
been cut through at depths of two or three hundred feet beneath the surface. But 
there does not appear to be any well-ascertained variation between their width so far 
below ground and at the surface. In not a few cases, indeed, dykes are met with in 
the lower workings of the coal-pits which do not reach the surface or even the workings 
in the higher coals. Such upward terminations of dykes will be afterwards considered, 
and it will be shown that towards its upper limit a dyke may rapidly diminish in width. 

(6) More definite information, and often from a wider vertical range, is to be gathered 
on coast-cliffs and in hilly districts, where the same dyke can be followed through a 
vertical range of several hundred feet. But so far as my own observations go, no 
general rule can be established that dykes sensibly vary in width as they are traced 
upward. Every one who has visited the basalt precipices of Antrim or the Inner 
Hebrides, where dykes are so numerous, will remember how uniform is their breadth as 
they run like ribbons up the faces of the escarpments.* Now and then one of them may 
be observed to die out, but in such cases (which are far from common among true dykes) 
the normal width is usually maintained up to within a few feet of the termination. 

All over the southern half of Scotland, where the dykes run along the crests of the 
hills and also cross the valleys, a difference of level amounting to several hundred feet may 
often be obtained between adjacent parts of the same dyke. But the breadth of igneous 
rock is not perceptibly greater in the valleys than on the ridges. The depth of boulder 
clay and other superficial deposits on the valley bottoms, however, too frequently conceals 
the dykes at their lowest levels. Perhaps the best sections in the country for the study 
of this interesting part of dyke-structure are to be found among the higher hills of the 
Inner Hebrides, such as the quartzites of Jura and the granophyres and gabbros of Skye. 
On these bare rocky declivities, numerous dykes may be followed from almost the sea- 
level up to the rugged and splintered crests, a vertical distance of between 2000 and 
3000 feet. The dykes are certainly not as a rule sensibly less in width on the hill tops 
than in the glens. So far, therefore, as I have been able to gather the evidence, there 
does not appear to me to be, as a general rule, any appreciable variation in the width of 
dykes for at least 2000 or 3000 feet of their descent. The fissures which they filled must 
obviously have had nearly parallel walls for a long way down. 

§ 6. Interruptions of Lateral Continuity. 

In tracing the great single dykes across the country, the geologist is often surprised 
to meet with gaps, varying in extent from a few hundred feet to several miles, in which 
no trace whatever of the igneous rock can be detected at the surface. This dis- 
appearance is not always explicable by the depth of the cover of superficial accumulations; 

* This point did not escape the attention of that excellent observer, Berger, in his examination of the dykes in 
the north of Ireland. We find him expressing himself thus : — "The depth to which the dykes descend is unknown; 
and after having observed the sections of a great many along the coast in cliffs from 50 to 400 feet in height, I have not 
been able to ascertain (except in one or two cases) that their sides converge or have a wedgeform tendency" (Trans. 
Geol. Soc, iii. p. 227). 



48 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

for it may be observed over ground where the naked rocks come almost everywhere to 
the surface, and where, therefore, if the conspicuous material of the dykes existed, it 
could not fail to be found. No dyke supplies better illustrations of this discontinuity 
than that of Cleveland. Traced north-westward across the Carboniferous tracts that 
lie between the mouth of the Tees and the Vale of the Eden, this dyke disappears some- 
times for a distance of six or eight miles. In the mining ground round the head of 
the South Tyne the rocks are bare, so that the absence of the dyke among them 
can only be accounted for by its not reaching the surface. Yet there can be no doubt 
that the various separated exposures, which have the same distinctive lithological characters 
and occur on the same persistent line, are all portions of one dyke which is continuous 
at some depth below ground. We have thus an indication of the exceedingly irregular 
upward limit of the dykes, as will be more particularly discussed further on. 

But there are also instances where the continuity is interrupted and then resumed 
on a different line. One of the best illustrations of this character is supplied by the 
large dyke which rises through the hills about a mile south of Linlithgow and runs 
westward across the coal-field. At Blackbraes it ends off in a point, and is not found 
again to the westward in any of the coal-workings. But little more than quarter of a 
mile to the south a precisely similar dyke begins, and strikes westward parallel to the 
line of the first one. The two separated strips of igneous rock overlap each other for 
about three-quarters of a mile. But that they are merely interrupted portions of what 
is really a single dyke can hardly be questioned. A second example is furnished by 
another of the great dykes of the same district, which after running for about 12 miles 
in a nearly east and west direction suddenly stops at Chryston, and begins again in the 
same direction, but on a line about a third of a mile further north. Such examples 
serve to mark out irregularities in the great fissures up which the materials of the 
dykes rose. 

§ 7. Length. 

In those districts where the small and crowded dykes of the gregarious type 
are developed, one cannot usually trace them for more than a short distance. The 
longest examples known to me are those which have recently been mapped with much 
patience and skill by Mr Clough in Eastern Argyleshire. Some of them he has been 
able to track over hill and valley for four or five miles, though the great majority are 
much shorter. In Arran and in the Inner Hebrides, it is seldom possible to follow what 
we can be sure is the same dyke for more than a few hundred yards. This difficulty 
arises partly, no doubt, from the frequent spread of peat or other superficial accumulation 
which conceals the rocks, and partly also from the great number of dykes and the want 
of sufficiently distinct lithological characters for the identification of any particular one. 
But making every allowance for these obstacles, we are compelled, I think, to regard the 
gregarious dykes as essentially short as well as relatively irregular. 

In striking contrast to these, come the great solitary dykes. In estimating their 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 49 

length, as I have already remarked, we must bear in mind the fact that they occasionally 
undergo interruptions of continuity owing to the local failure of the igneous material to 
rise to the level of what is now the surface of the ground. A narrow wall-like mass of 
augite-andesite, dolerite, or basalt which sinks beneath the surface for a few hundred 
yards, or for several miles, and reappears on the same line with the same petrographical 
characters, while there may be no similar rock for miles to right and left, can only be one 
dyke prolonged underneath in the same great line of fissure. But even if we restrict our 
measurements of length to those dykes or parts of dykes where no serious interruption of 
continuity takes place, we cannot fail to be astonished at the persistence of these strips 
of igneous rock through the most diverse kinds of geological structure. A few illustrative 
examples of this feature may be selected. It will be observed that the longest and 
broadest dykes are found furthest from the basalt-plateaux, while the shortest and 
narrowest are most abundant near these plateaux. 

Not far from what I have taken provisionally as the northern boundary of the dyke 
region, two dykes occur which have been mapped from the head of Loch Goil by 
Arrochar across Lochs Lomond and Katrine by Ben Ledi to Glen Artney, whence they 
strike into the Old Eed Sandstone of Strathmore, and run on to the Tay near Perth— a 
total distance of about 60 miles. If the dyke which continues in the same line on the 
other side of the estuary of the Tay beyond Newburgh, is a prolongation of one of these, 
then its entire length exceeds 70 miles. A few miles further south, one of a group of 
dykes can be followed from the heart of Dumbartonshire by Callander across the Braes of 
Doune to Auchterarder — a distance of 47 miles, with an average breadth of more than 
100 feet. In the district between the Forth and Clyde a number of long parallel dykes 
can be traced for many miles across hill and plain, and through the coal-fields. One of 
these is continuous for 25 miles from the heart of Linlithgowshire into Lanarkshire. 
Still longer is the dyke which runs from the Firth of Forth at Grangemouth westward 
to the Clyde, opposite Greenock — a distance of about 36 miles. Coming southward, we 
encounter a striking series of single dykes on the uplands between the counties of 
Lanark and Ayr, whence they strike into the Silurian hills of the southern counties. 
One of these runs across the crest of the Haughshaw Hills, and can be followed for some 
30 miles. But if, as is probable, it is prolonged in one of the dykes that traverse the 
moorlands of the north of Ayrshire and south of Renfrewshire to the Clyde, its actual 
length must be at least twice that distance. The great Moffat and Eskdale dyke strikes 
for more than 50 miles across the south of Scotland and north of England. The Hawick 
and Cheviot dyke runs for 26 miles in Scotland and for 32 miles in Northumberland. 
But the most remarkable instance of persistence is furnished by the Cleveland dyke. 
From where it is first seen near the coast-cliffs of Yorkshire it can be followed, with frequent 
interruptions, during which for sometimes several miles no trace of it appears at the 
surface, across the north of England and as far as Dalston Hall south of Carlisle, beyond 
which the ground onwards to the Solway Firth is deeply covered with superficial deposits. 
The total distance through which this dyke can be recognised is about 110 miles. But 



50 DR UE'lKIE ON THE HISTORY OF VOLCANIC ACTION 

it probably goes much further still. On the opposite side of the Solway, a dyke which 
runs in the same line, rises through the Permian strata a little to the east of the 
mouth of the Nith. Some miles further to the north-west, near Moniaive, Mr J. Horne, 
in the progress of the Geological Survey, traced a dark compact dyke with kernels of 
basalt-glass near its margin, running in the same north-westerly direction. Still further 
on in the same line, another similar rock is found high on the flanks of the lofty hill 
known as Windy Standard. And lastly, in the Ayrshire coal-field, a dyke still continuing 
the same trend, runs for several miles, and strikes out to sea near Prestwick. It cannot, 
of course, be proved that these detached Scottish protrusions belong to one great dyke, or 
that if such a continuous dyke exists, it is a prolongation of that from Cleveland. At 
the same time, I am on the whole inclined to connect the various outcrops together as 
those of one prolonged subterranean wall of igneous rock. The distance from the last 
visible portion of the Cleveland dyke near Carlisle to the dyke that runs out into the 
Firth of Clyde near Prestwick, is about 80 miles. If we consider this extension as a 
part of the great north of England dyke, then the total length of this remarkable 
geological feature will be about 190 miles. 

§ 8. Persistence of Mineral Characters. 

Not less remarkable than their length is the preservation of their normal petrographical 
characters by some dykes for long distances. In this respect the Cleveland dyke may 
again be cited as a typical example. The macroscopic and microscopic structures of 
the rock of this dyke distinguish it among the other eruptive rocks of the north of 
England. And these peculiarities it maintains throughout its course.* Similar though 
less prominent uniformity may be traced among the long solitary dykes of the south of 
Scotland, the chief variations in these arising from the greater or less extent to which 
the original glassy magma has been retained. The same dyke will at one part of its 
course show abundant glassy matter even to the naked eye, while at a short distance the 
vitreous ground-mass has been devitrified, and its former presence can only be detected 
with the aid of the microscope. 

§ 9. Direction. 

Another characteristic feature of the dykes is their generally rectilinear course. 
So true are they to their normal trend that, in spite of varying inequalities of surface 
and wide diversities of geological structure in the districts which they traverse, they 
run over hill and dale almost with the straightness of lines of Eoman road. In the 
districts where they assume the gregarious type, and depart most widely from the character 
of the great solitary dykes, they still tend to run in straight or approximately straight 
lines, or, if wavy in their course, to preserve a general parallelism of direction. 

Yet even among the great persistent dykes instances may be cited where the recti- 
linear trend is exchanged for a succession of zig-zags, though the normal direction is 

* See the careful examination of this dyke by Mr Teall, Quart. Jour. Geol. Soc, xl. p. 209. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 51 

on the whole maintained. In such cases, it is evident that the fissures were not long 
straight dislocations like the larger lines of fault in the earth's crust, but were rather 
notched rents or cracks which, though keeping on the whole one dominant direction, were 
continually being deflected for short distances to either side. As a good illustration of 
this character, reference may be made to the Cheviot and Hawick dyke. In Teviotdale 
this dyke can be followed continuously among the rocky knolls, so that its deviations 
can be seen and mapped. From the median line of average trend the salient angles 
sometimes retire fully a quarter of a mile on either side. Some examples of the same 
feature may be noticed in the Eskdale dyke. The large dyke which runs westward from 
Dunoon has been observed by Mr Clough to change sharply in direction three times in 
four miles, running sometimes for a short distance at a right angle to its general 
direction (see fig. 17). 

Among these solitary dykes also, though the persistence of their trend is so pre- 
dominant, there occur instances where the general direction undergoes great change. 
Some of the most remarkable cases of this kind have been mapped by Mr B. N. Peach 
and Mr R. L. Jack, in the course of the Geological Survey of Perthshire. Several 
important dykes strike across the Old Red Sandstone plain for many miles in a direction 
slightly south of west. But when they approach the rocks of the Highland border in 
Glen Artney, they bend round to south-west, and continue their course along that new line. 

In my early paper on the " Chronology of the Trap-Rocks of Scotland," * I called 
attention to the dominant trend of the dykes from N.W. to S.E. Subsequent 
research has shown this to be on the whole the prevalent direction throughout the 
whole region of dykes. But the detailed mapping, carried on by my colleagues and 
myself in the Geological Survey, has brought to light some curious and interesting 
variations from the normal trend. In the districts where dykes of the gregarious type 
abound there is sometimes no one prevalent direction, but the dykes strike to almost 
all points of the compass. Of the Arran dykes, so carefully catalogued by Necker, only 
about a third have a general north-westerly course. But in Eastern Argyleshire the 
abundant dykes mapped by Mr Clough trend almost without exception towards N.N.W. 
In the north of Ireland Berger found the direction of thirty-one dykes to vary from 
17° to 71° W. of N., giving a mean of N. 36° W.t In Islay, Jura, Eigg, Mull, and Skye 
the mean of several hundred observations has given me similar results. 

It appears therefore that though there is sometimes extraordinary local diversity in 
the direction of the dykes in those districts where they present the gregarious type, the 
general north-westerly trend can usually still be recognised. But when we turn to the long 
massive solitary dykes, we soon perceive a remarkable change in their direction as we 
follow them northward into Scotland. In the paper just referred to, I pointed out how 
the general north-westerly trend becomes east and west in the Lothians, with a tendency 
to veer a little to the south of west and north of east. This departure from the normal 
direction is now seen to be part of a remarkable radial arrangement of the dykes. 

* Trans. Roy. Soc. Edin., xx. p. 650. t Trans. Geol. Soc, iii. p. 225. 



52 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

Beginning at the southern margin of the dyke-region, we have the notable example of 
the Cleveland dyke, which in its course from Cleveland to Carlisle runs nearly W. 15° N. 
The Eskdale dyke has an average trend of W. 32° N., and the same general direction is 
maintained by the group of dykes which run from the Southern Uplands across the south- 
west of Lanarkshire and north-east of Ayrshire. But as we proceed northwards we 
observe the trend to turn gradually round towards the west. The dyke that runs from 
near the mouth of the Coquet across the Cheviot Hills to beyond Hawick has a general 
course of W. 8° N. In the great central coal-field of Scotland the average direction may 
be taken to be nearly E. and W., the same dyke running sometimes to the north, and 
sometimes to the south of that line. But immediately to the north a decided tendency 
to veer round southwards makes its appearance. Thus the long dyke which runs from the 
Carse of Stirling through the Campsie Fells to the Clyde west of Leven, has a mean direction 
of W. 5° S. This continues to be the prevalent trend of the remarkable series of 
dykes which crosses the Old Red Sandstone plains, though some of these revert in whole 
or in part to the more usual direction by keeping a little to the north of west. Even as 
far as Loch Tay and the head of Strathardle, the course of the dykes continues to be to 
the south of west. Tracing these lines upon a map of the country we perceive that they 
radiate from an area lying along the eastern part of Argyleshire and the head of the 
Firth of Clyde (see Plate I.). 



§ 10. Termination Upwards. 

It was pointed out many years ago by Winch that some of the dykes which traverse 
the Northumberland coal-field do not cut the overlying Magnesian Limestone. The 
Hett dyke, south of Durham, which no doubt belongs to the ancient series of igneous 
protrusions already referred to, is said to end off abruptly against the floor of the 
limestone.* Here and there, among the precipices of the Inner Hebrides, a dyke may 
be seen to die out before it reaches the top of the cliff. But in the vast majority of 




Fig. 6. —Section along the line of the Cleveland Dyke at Cliff Ridge, Guisbrough (G. Barrow), scale, 12 inches to 1 mile. 

cases, no evidence remains as to how the dykes terminated upwards. I have referred to 
the occasional interruptions of the continuity of a dyke, where, though the rock does not 
reach the surface, it must be present in the fissure underneath. Such interruptions 
show that, in some places at least, there was no rise of the rock even up to the level of 
what is now the surface of the ground, and that the upward limit of the dykes must 
have been exceedingly irregular. 

* This is expressed in the Geological Survey map, Sheet 93, N.E. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



53 



pq 






pq 





P5 



53 -M 
2 >> 



-k_ 



\ 



A 



If 



■A 



"K 



"fe 



ft A! 






Excellent illustrations of this feature are supplied by sections on the line of the 
Cleveland dyke. Towards its south-eastern extremity this ►. i % % % % 

great band of igneous rock ascends from the low Triassic L ~~' " 

plain of the Tees into the high uplands of Cleveland. Its 
course across the ridges and valleys there has been carefully 
traced for the Geological Survey by Mr G. Barrow, who has 
shown that over certain parts of its course it does not reach 
the surface, but remains concealed under the Jurassic rocks, 
which it never succeeded in penetrating. But that in places 
it comes within a few feet of the soil is shown by the baked 
shale at the surface, for the alteration which it has induced 
on the surrounding rocks only extends a few feet from its 
margin. These interruptions of continuity show how uneven 
is the upper limit of the dyke. The characteristic porphyritic 
rock may be observed running up one side of a hill to the 
crest, but never reaching the surface on the other side. At 
Cliff Eidge, for example, about three miles south-west of 
Guisbrough, Mr Barrow has followed it up to the summit 
on the west side ; but has found that on the east side it does 
not pierce the shales, which there form the declivity. This 
structure is represented in fig. 6. The vertical distance 
between the summit to the left, where the dyke (b) disappears, 
and the point to the right, where the Lias shale (a) of the 
hill-side is concealed by drift (c), amounts to 250 feet, the 
horizontal distance being a little more than 900 feet. But 
as the shale when last seen at the foot of the slope is quite 
unaltered, the dyke must there be still some little distance 
beneath the surface, so that the vertical extension of this 
upward tongue of the dyke must be more than 250 feet. Mr 
Barrow, to whom I am indebted for these particulars, has 
also drawn the accompanying section (fig. 7) along the course 
of the dyke for a distance of nearly 1 1 miles eastward from 
the locality represented in fig. 6. From this section, it will 
be observed that in that space there are at least three tongues 
or upward projections of the upper limit of the dyke. Several 
additional examples of the same structure are to be seen 
further east towards the last visible outcrop of the dyke. 

Another feature connected with the upward termination 
of the dyke is well seen in some parts of the ground through 
which the two foregoing sections are taken. Mr Barrow 
informs me that at Ayton a level course has been driven 

VOL. XXXV. PART 2. 






C3 —3 






O 



o 



o 



a e| 










into the hill for mining 



H 



54 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



operations, at a height of 400 feet above sea-level, and the dyke has there been ascer- 
tained to be 80 feet broad. Higher on the hill, close to the 750 feet contour-line, its 
breadth is only 20 feet, so that it narrows upward as much as 60 feet in a vertical height 
of 350 feet. Its contraction in width during the last twenty feet is still more rapid, and 
in the last few yards it diminishes to two or three feet, and has a rounded top over which 
the strata are bent upward. The accompanying section (fig. 8) across the upper part of 
the dyke will make these features clearer. 

Further to the west an exposure of the upper limit of the dyke has been described 
and figured by Mr Teall. In 1882, at one of the Cockfield quarries (fig. 9), the dyke 









Fig. 8. — Section across the extreme upper limit of the Cleveland 
Dyke, Ayton, on the scale of 20 feet to one inch (G. Barrow). 
a, Jurassic shales, &c. ; b, Dyke. 



a b 

Fig. 9. — Upper limit of the Cleveland Dyke in 
quarry near Cockfield (after J. J. H. Teall). 
a, a, Carboniferous shales ; b, Dyke. 



was "seen to terminate upwards very abruptly in the form of a low and somewhat 
irregular dome, over which the Coal Measure shales passed without any fracture, and only 
with a slight upward arching." * 

Near the other or north-western termination of this great dyke, similar evidence is 
found of an uneven upper limit. After an interrupted course through the Alston moors, 
the dyke reaches the ground that slopes eastward from the edge of the Cross Fell 
escarpment. Its highest visible outcrop is at a height of 1 700 feet. But westwards from 
that point the dyke disappears under the Carboniferous rocks, and does not emerge along 
the front of the great escarpment that descends upon the valley of the Eden, where among 
the naked scarps of rock it would unquestionably be visible if it reached the surface. 
Its upper edge must rapidly descend somewhere behind the face of the escarpment, 
for the igneous rock crops out a little to the west of the foot of the cliff, at a height of 
about 1000 feet below the point where it is last seen on the hills above. Here the top 
of the dyke has a vertical drop of not less than 1000 feet, in a horizontal distance of 
five miles, as shown in fig. 10, which has been drawn for me by Mr J. G. Goodchild. 

* Quart. Jour. Geol. Soc, xl. p. 210. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



55 



It will be observed that in these sections (figs. 7 and 10) there is 
a curiously approximate coincidence between the inequalities in the 
upper surface of the dyke and those in the form of the overlying 
ground. The coincidence is too marked and too often repeated to be 
merely accidental. Whether the ancient topographical features had 
any influence in determining, by cooling or otherwise, the limit of the 
upward rise of the lava, or whether the dyke, even though concealed, 
has affected the progress of the denudation of the ground overlying 
it, is a question worthy of fuller investigation. 



w 



T3 



§ 11. Known Vertical Extension. 

Closely connected with the determination of the upper limit reached 
by the dykes, is the total vertical depth to which they can be traced. 
Of course, the depth of the original reservoir of molten rock which 
supplied them remains unknown, and probably undiscoverable. But 
it is possible in many cases to determine at least the inferior limit of 
the thickness of rock through which the molten material of the dykes 
has ascended. In the dark gabbro hills of Skye, numerous dykes may 
be seen climbing from the glens right up the steep rugged acclivities 
and over the crests. In these and similar cases, we can actually trace 
the dykes through a vertical thickness of more than 3000 feet of 
rock. The dykes which cross Loch Lomond and ascend the hills on 
either side of that deep depression must rise through at least as great 
a thickness. But where a knowledge of the geological structure of the 
ground enables us to estimate the bulk of the successive rock-formations 
which underlie the surface, it can be shown that the lava ascended 
through a much greater depth of rock. Measurements of this kind 
can best be made towards the eastern end of the Cleveland dyke, where 
the different sedimentary groups have not been seriously disturbed, and 
where from natural sections and artificial borings their thicknesses are 
capable of satisfactory computation. The highest bed of the Jurassic 
series anywhere touched by the dyke is the Cornbrash. It is certain, 
therefore, that the igneous rock rises through all the subjacent members 
of the Jurassic series up to that horizon. There can be no doubt also 
that the Trias and Magnesian Limestone continue in their normal 
thickness underneath the Jurassic strata. To what extent the Coal- 
Measures exist under Cleveland has not been ascertained ; possibly 
they have been entirely denuded from that area, as from the ground 
to the west. But the Millstone Grit and Carboniferous Limestone pro- 
bably extend over the district in full development ; and below them 
there must lie a vast depth of Upper and Lower Silurian strata, 



&0 



S 



H 



o 



ni g 



A 
H 



13 ° 



o w 

O <D 

si § 

-4-> S-< 

a -m 

a> o 

a a 

— . to 

S-i <D 
ci o 

cq ° 

<D a) 

V> J?? 

« 2 
m -a 
O -^ 

O 2 

cd 
<u ?• 

2 S 

s a 

>> M 

O .5 

-X3 >? 

a> o 
&* .^ 

O & 

V n-l 

°J 

g a 

S * 
O a> 

« ,a 

CD *" 



M 

a 
o 





f3 



56 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



probably also of still older Palaeozoic rocks, and beneath all the thick Archaean platform. 
Tabulating these successive geological formations, and taking only the ascertained 
thickness of each in the district, we find that they give the results shown in the 
subjoined table.* 



Feet. 



Strata Cut by the Cleveland Dyke. 

Cornbrash — 

Lower Oolite and Upper Lias, as proved by bore-hole on Gerrick Moor, . . . 950 

Middle and Lower Lias, ascertained from measurement of cliff-sections and from mining 

operations to be more than ........ 850 

New Red Sandstone and Marl, found by boring close to the Tees to exceed 
Magnesian Limestone, at least 
Coal-Measures, possibly absent 



Millstone Grit, not less than 
Carboniferous Limestone series, at least 
Silurian rocks, probably not less than 



1,600 

500 



500 

3,000 

10,000 

17,400 



There is thus evidence that this dyke has risen through probably more than three 
miles of stratified rocks. How much deeper still lay the original reservoir of molten 
material that supplied the dyke we have at present no means of computing. 



§ 12. Branches and Veins. 

It might have been anticipated that the uprise of such abundant masses of 
molten rock in so many long and wide fissures would generally be attended with 
the intrusion of the same material into lateral rents and irregular openings, so that 
each dyke would have a kind of fringe of offshoots or processes striking from it 
into the surrounding ground. It might have been expected also that dykes would often 
branch, and that the arms would come together again and enclose portions of the rocks 
through which they rise. But in reality such excrescences and bifurcations are of 
comparatively rare occurrence. As a rule, each dyke is a mere wall of igneous rock, with 
little more projection or ramification than may be seen in a stone field-fence. Among 
the short, narrow, and irregular dykes of the gregarious type branchings are occasionally 
seen, and in some districts are extraordinarily abundant. But among the great single 
dykes such irregularities are far less common than might have been looked for. A 
few characteristic examples from each type of dyke may here be given. 

The Cleveland dyke, which in many respects is typical of the great solitary dykes of 
the country, has been traced for many miles without the appearance of a single offshoot 
of any kind. Yet here and there along its course it departs from its usual regularity. 
As it crosses the Carboniferous tracts of Durham and Cumberland, there appear near its 
course lateral masses of eruptive rock, most of which doubtless belong to the much older 
" Whin Sill." But there is at least one locality, at Bolam near Cockfield, in the county 

* Drawn up for nie by Mr Barrow. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 57 

of Durham, where the dyke, crossing the Millstone Grit, suddenly expands into a boss, and 
immediately contracts to its usual dimensions. Around this knot several short dykes 
or veins seem to radiate from it. The dyke has been quarried here, and its relations to 
the surrounding strata have been laid bare, as will be again referred to a little further 
on. # 

Among the great persistent dykes of Scotland the absence of bifurcation and lateral 
offshoots offers a striking contrast to the behaviour of the dykes in those districts where 
they are small in size and many in number. But exceptions to the general rule may be 
gathered. Thus the Eskdale dyke is flanked at West Carrick with a large lateral vein, 
which is almost certainly connected with the main fissure. The Hawick and Cheviot 
dyke splits up on the hill immediately to the east of the town of Hawick, sends off some 
branches, and then resumes its normal course (fig. 11). Again, one of the two nearly 
parallel dykes which run from Loch Goil Head across Ben Ledi into Glen Artney 
bifurcates at the foot of that valley, its northern limb (about two miles long) speedily 




Fig. 11. — Branching portion of the great Dyke near Fig. 12. — Branching Dyke at foot of Glen Artney (length 

Hawick (length about 1 mile). about 4 miles). 

dying out, and its southern branch throwing off another lateral vein, and then continuing 
eastward as the main dyke (fig. 12). 

In the districts of gregarious dykes, however, abundant instances may be found of 
dykes that branch, and of others that lose the parallelism of their walls, become irregular 
in breadth, direction, and inclination, so as to pass into those intrusive forms that are 
more properly classed as veins. Excellent illustrations of bifurcating dykes may be 
observed along the shores of the Firth of Clyde, particularly on the eastern coast line of 
the isle of Arran. The venous character has been familiar to geologists from the sketches 
given by Macculloch from the lower parts of the cliffs of Trotternish in Skye.t But 
still more striking examples are to be seen in the breaker-beaten cliffs of Ardnamurchan. 
The pale Secondary limestones and calcareous sandstones of that locality are traversed by 
a series of dark basic veins, and the contrast of tint between the two kinds of rock is 
so marked as even to catch the eye of casual tourists in the passing steamboats. The 

* This locality was well described by Sedgwick, in his early paper on Trap-Dykes in Yorkshire and Durham, Trans. 
Cambridge Phil. Soc, ii. p. 27. 
t Western Islands, plate xvii. 



58 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



veins vary in width from less than an inch to several feet or yards. They run in all 
directions and intersect each other, forming such a confused medley as requires some 
patience on the part of the geologist who would follow out each independent ribbon of 
injected material in its course up the cliffs, or still more, would sketch their ramifications 
in his note-book. A good, though perhaps somewhat exaggerated, illustration of their 
general character was given by Macculloch.* The accompanying figure (fig. 13) is less 
sensational, but represents with as much accuracy as I could reach, the network of veins 
near the foot of the cliffs. One conspicuous group of veins, which seen from a distance 
looks like a rude sketch of a lug-sail traced in black outline upon a pale ground, is known 
to the boatmen as " M'Niven's Sail." 

As a general rule, the narrower the vein the finer in grain is the rock of which it 
consists. This compact dark homogeneous material has commonly passed by the name 




Fig. 13. — Basic Veins traversing Secondary Limestone and Sandstone on the coast cliffs, Ardnamurchan. 



of " basalt," but its minuteness of texture probably in most cases arises from local 
rapidity of cooling, and it may be the same substance which, where in larger mass in the 
immediate neighbourhood, has solidified as one of the other pyroxene-plagioclase- 
magnetite rocks. 

With regard to the places where such abundant tortuous veins are more especially 
developed, I may remark that they are particularly prominent under a thick overlying mass 
of erupted rock, such as a great intrusive sheet, or the bedded basalts of the plateaux, or 
where there is good reason to believe that such a deep cover, though now removed by 
denudation, once overspread the area in which they appear. It will be shown in the 
sequel that such horizons have been peculiarly liable to intrusions of igneous material of 
various kinds, and at many different intervals, during the volcanic period. A thick cake 

* Op. cit., plate xxxiii. fig. 1. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 59 

of crystalline rock seems to have offered such resistance to the uprise of molten material 
through it, that when the subterranean energy was not sufficient to rend it open by great 
fissures, and thus give rise to dykes, the lavas were forced into such irregular cracks as 
were made partly in the softer rocks underneath and partly in the cake itself, or found 
escape along pre-existing divisional planes. In Ardnamurchan, round the Cuillin Hills of 
Skye, and in Rum, the overlying resisting cover now consists mainly of gabbro sheets. In 
the east of Skye, in Eigg, and in Antrim, it is made up of the thick mass of the plateau- 
basalts. 

§ 13. Connection op Dykes with Intrusive Sheets. 

Every field-geologist is aware how seldom he ean actually find the vent or pipe up 
which rose the igneous rock that now forms those massive beds which he denominates 
intrusive sheets. He might well be pardoned were he to anticipate that, in a 
district much traversed by dykes, there should be many examples of intrusive sheets 
and frequent opportunities of tracing their connection with the fissures from which 
their material might be supposed to have been supplied. But such an expectation 
is singularly disappointed by an actual examination of the Tertiary volcanic region 
of Britain. That there are many intrusive sheets belonging to the great volcanic 
period with which I am now dealing, I shall endeavour to show in the sequel. But 
it is quite certain that though these sheets have of course each had its subterannean 
pipe or fissure of supply, they can only in very rare instances be directly traced to 
the system of dykes. On the other hand, the districts where great single dykes are 
most conspicuous, are for the most part free from intrusive sheets, except those of 
much older date, like the Carboniferous Whin Sill of Durham and the diabases of 
Linlithgowshire. 

Yet a few interesting examples of the relation of dykes to sheets have been noticed. 
The earliest observed instances were those figured and described by Macculloch in his 
Western Islands of Scotland. Among them one has been familiar to geologists from 
having done duty in text-books of the science for more than half a century. I allude to 
the diagram of " Trap and Sandstone near Suishnish."* In that drawing seven dykes are 
shown as rising vertically through the horizontal sandstone, and merging into a thick 
overlying mass of " trap." The author in his explanation leaves it an open question 
" whether the intruding material has ascended from below and overflowed the strata, or 
has descended from the mass," though from the language he uses in his text we may 
infer that he was inclined to regard the overlying body as the source of the veins below 
it.t 

The section given by Macculloch, however, does not quite accurately represent the 
facts. The narrow dykes there drawn have no connection with the overlying sheet, but 
are part of the abundant series of basaltic dykes found all over Skye. The feeder of the 
sheet was undoubtedly the thick dyke which descends the steep bank immediately on the 

* Op. cit., pi. xiv. fig. 4. t Vol. i. pp. 384, 385. 



60 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



southern front of Cam Dcarg (636 feet high). The accompanying figure (fig. 14) shows 
what I believe to be the true geological structure of the locality, but the actual junction 
of the dyke and sheet is concealed under the talus of the slope. I shall have occasion in 
a later part of this paper to refer again to this section in connection with the history 
of intrusive sheets. 

Sedgwick, in the paper already quoted, gave an account and figure of the expansion 
of the Cleveland dyke at Bolam, to which allusion has already been made. He showed 
that from a part of the dyke which is unusually contracted a great lateral extension of 
the igneous rock takes place on either side over beds of shale and coal. While in the 
dyke the prisms are as usual directed horizontally inward from the two walls, those in 
the connected sheet are vertical, and descend upon the surface of highly indurated 
strata on which the sheet rests. 

But by far the most important examples known to me are those which occur in the 
coal-field of Stirlingshire. In that part of the country, the remarkable group of dykes 
already referred to, lying nearly parallel to each other and from half a mile to about 




Fig. 14. — Section showing the connection of a Dyke with an Intrusive Sheet, Point of Suisnish, Skye. g, Granophyre of 
Cam Dearg ; /, similar rock, which appears eastward under the "sill" (d) ; e, intrusive sheet of fine-grained "basalt" ; 
d, intrusive sheet or "sill " of coarse dolerite, 200 feet thick at its maximum, and rapidly thinning out ; c, dyke or pipe of 
finer grain than d ; b, yellowish-brown shaly sandstones, and a, dark sandy shales (Lias). 



three miles apart, runs in a general east and west direction. From one of these dykes no 
fewer than four sheets or " sills" strike off into the surrounding Coal-Measures. The 
largest of them stretches southwards for three miles, but the same rock is probably con- 
tinued in a succession of detached areas which spread westwards through the coal-field 
and circle round to near the two western sheets that proceed from the same dyke. 
Another thick mass of similar rock extends on the north side of the dyke for two and a 
half miles down the valley of the river Avon. These various processes, attached to or 
diverging from the dyke, are unquestionably intrusive sheets, which occupy different 
horizons in the Carboniferous series. The one on the north side has inserted itself a little 
above the top of the Carboniferous Limestone series. Those on the south side lie on 
different levels in the Coal-Measures, or rather they pass transgressively from one 
platform to another in that group of strata. 

No essential difference can be detected by the naked eye between the material of the 
dyke and that of the sheets. If a series of specimens from the different exposures were 
mixed up it would be impossible to separate those of the dyke from those of the sheets. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



61 



A microscopical examination of the specimens likewise shows that they are perfectly 
identical in composition and structure, chiefly referable to rocks of the dolerite type, but 
partly to the tholeiite type. I have therefore no doubt that these remarkable 
appendages to this dyke are truly offshoots from it, and are not to be classed with the 
general mass of the diabases of central Scotland, which are Lower Carboniferous. The 
accompanying diagrammatic section (fig. 15) explains what appears to me to be the 
structure of the ground. 

An interesting and important fact remains to be stated in connection with these 
sheets. They are traversed by some of the other east and west dykes. This is particu- 
larly observable in the case of the sheet which extends northwards from the dyke through 




Fig. 15. 



-Section to show the connection of a Dyke with an Intrusive Sheet, Stirlingshire Coal-field, a, Dyke in line of fault : 
b, intrusive sheet traversing and altering the coals ; i, Slaty-band Ironstone. 



the parish of Torphichen. Two well-marked dykes can be seen running westwards 
among the ridges of the sheet. It is obvious, therefore, that these particular dykes are 
younger than the sheet. But, as will be shown in the sequel, there is abundant evidence 
that all the dykes of a district are not of one eruption. The intersection of one eruptive 
mass by another does not necessarily imply any long interval of time between them. 
They mark successive, but it may be rapidly successive, manifestations of volcanic action. 
Hence the cutting of the sheets by other dykes does not seem to me to invalidate the 
identification of these sheets as extravasations from the great dyke by which they are 
bounded. 

§ 14. Intersections of Dykes — Repeated Dykes in the same Line of Fissure. 

Innumerable instances may becited, where one dyke or one set of dykes cuts across 
another. To some of these I shall refer in discussing the data for estimating the relative 
age of dykes. In considering the intersection from the point of view of geological 
structure, we are struck with the clean sharp way in which it so generally takes place. 
The rents into which the younger dykes have been injected seem, as a rule, not to have 
been sensibly influenced in width or direction by the older dykes, but go right across 
them. Hence the younger dykes retain their usual breadth and trend (fig. 16). The 
most interesting examples are those in which one dyke runs along another, as may 
occasionally be observed in the west of Scotland."" In these cases, which are to be 
distinguished from those where the whole may be really a portion of one original slowly 
cooling mass, the central dyke differs sufficiently in texture and structure to be discrimin- 

* Macculloch figured an example from Strathaird, Western Islands, pi. xviii. fig. 1. Mr Clough has found some 
good instances in south-eastern Argyleshire. 

VOL. XXXV. PART 2. I 



62 



DR GETKIE ON THE HISTORY OF VOLCANIC ACTION 




IIP 

Fig. 16. — Intersection of Dykes in bedded 
basalt, Caliach Point, Mull. 



ated from that which it has invaded. Its rock is generally rather fine-grained, some- 
times decidedly porphyritic, and in many cases is a true basalt. Where it is broad 

enough to show the difference between margin and 
centre, its outer edges present the usual finer grain. 
There can be no doubt that the older dyke has been 
actually split open, and fresh eruptive material has 
risen along the fissure. 

If the subterranean movements were energetic 
enough to split up an already consolidated dyke, so as 
to allow of the renewed uprise of molten material between 
the separated portions, we may believe that much more 
frequently the opening would be effected not along the 
middle of the dyke, but between the dyke and one of its 
fissure walls. I have observed examples of this structure 
in the Western Islands, and Mr Clottgh has recently 
found a number in Argyleshire. If the section is limited 
in extent, we may be unable to determine which is the 
older of the two parallel bands of igneous rock, though 
the fact that they present to each other the usual fine- 
grained edge due to more rapid cooling, shows that they are not one but two dykes 
belonging to distinct eruptions. So far as I have noticed, where one of the dykes can 
be continuously traced for a considerable distance, the other is short, and cannot be 
recognised at other exposures of the more continuous one. I infer that the shorter 
one is the younger of the two. 

§ 15. Contact-Metamorphism of the Dykes. 

Another anticipation which a geologist might naturally entertain is, that these 
abundant intrusions of igneous rock should be accompanied with plentiful evidence 
of contact-metamorphism along their flanks. But in actual fact, evidence of any serious 
amount of alteration is singularly scarce. A slight induration of the rocks on either side 
of a dyke is generally all the change that can be detected. 

Some of the larger dykes, however, show more marked metamorphism, the nature of 
which is chiefly determined by the chemical composition of the rock affected. The most 
pronounced alteration is that which has been superinduced on carbonaceous strata, and 
particularly on seams of coal. In the Ayrshire coal-field the alteration of the coal extends 
sometimes 150 feet from the dyke, the extent of the change depending not merely on 
the mass of the igneous rock, but on the nature of the coal, and possibly on other causes. 
Close to a dyke, coal passes into a kind of soot or cinder, but sometimes assumes the 
form of a finely columnar coke.* Shales are converted into a hard flinty substance that 
breaks with a conchoidal fracture and rings under the hammer. Fire-clay is baked into a 

* Explanation of Sheet 22, Geol. Survey Scotland, p. 26. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 63 

porcelain-like material. Limestone is changed for a few inches into marble. Sandstones 
are indurated into a kind of quartzite, sometimes assume a columnar structure (the 
columns being directed away from the dyke-walls), and for several feet or yards have their 
yellow or red colours bleached out of them. The granite of Ben Cruachan where quarried 
on Loch Awe, as I am informed by Mr J. S. Grant Wilson of the Geological Survey, is 
traversed by a basic dyke, and for a distance of about 20 feet is rendered darker in 
colour, becomes granular, and cannot be polished and made saleable. 

These, however, are the extremes of contact-metamorphism by the Tertiary basic dykes. 
Let any geologist visit the Lias district of Skye, and he will not fail to be surprised at the 
almost entire absence of alteration in circumstances where he would have expected to find 
it. The dark shales, though ribbed across with hundreds of dykes, are sometimes hardly 
even hardened, and the limestones are not rendered in any appreciable degree more crystal- 
line even up to the very margin of the intrusive rock. Where the igneous material has 
been thrust between the strata in sheets, it has produced far more general and serious 
metamorphism than when it occurs in the form of dykes. The famous rock of Portrush, 
which was once gravely cited as an example of fossiliferous basalt, is a good illustration 
of the way in which Lias shale is porcellanised when the intruded igneous material has 
been thrust between its planes of bedding. 

In connection with the metamorphism superinduced by dykes, reference may be made 
to the curious alteration which they themselves have sometimes undergone where they 
have invaded a carbonaceous shale or coal. The igneous rock loses its dark colour and 
obviously crystalline structure, and becomes the pale-yellow or white, dull, earthy substance 
known to geologists as " white trap." The chemical changes involved in this alteration 
have been described by Sir I. Lowthian Bell. # Dr Stecher has also discussed the 
the alterations traceable by the aid of the microscope.t 

§ 16. Eelation of Dykes to the Geological Structure op the Districts 

which they traverse. 

In no respect do the Tertiary basic djdjes stand more distinguished from all the other 
rocks of this country than in their extraordinary independence of geological structure. 
The successive groups of Palaeozoic and Mesozoic strata follow each other in approximately 
parallel bands, which run obliquely across the island from south-west to north-east. The 
most important lines of fault take the same general line. The contemporaneously included 
igneous rocks follow, of course, the trend of the stratified deposits among which they lie, 
and even the intrusive eruptive rocks tend to group themselves along the general strike 
of the whole country. But the Tertiary dykes have their own independent direction, to 
which they adhere amid the extremest diversities of geological arrangement. 

* Proc. Roy. Soc, xxiii. (1875)*p. 543. 

t Tschermak's Mineralogische Mittheilungen, ix. (1887) p. 145; Proc. Boy. Soc. Edin., 1888. Dr Stecher's 
investigation is based upon a series of specimens from the intrusive (Carboniferous) rocks of the basin of the Firth of 
Forth, and has reference both to the phenomena of contact-metamorphism and the alteration of the eruptive rock ; 
but these changes belong to the Carboniferous period. 



64 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

In the first place, the dykes intersect nearly the whole range of the geological 
formations of the British Islands. In the Outer Hebrides and north-west Highlands, 
they rise through the most ancient Archaean gneisses, and through the red (Torridon) 
sandstones, which may be older than any of the Cambrian rocks of Wales. In the south 
of Scotland and north of England, they traverse the various subdivisions of the Lower 
and Upper Silurian system. In the southern Highlands, they pursue their course across 
the gnarled and twisted schists of the younger crystalline series. In the basins of the 
Tay, Forth, and Clyde they cross the plains and ridges of the Old Red Sandstone, with 
its deep pile of intercalated volcanic rocks. In central Scotland, and the northern 
English counties, they occur abundantly in the Carboniferous system, and have destroyed 
the seams of coal. In Cumberland and Durham, they traverse the Permian and Trias 
o-roups. In Yorkshire, and along the west of Scotland, they are found running 
through Jurassic strata. In Antrim, they intersect the Chalk. Both in the north of 
Ireland, and all through the chain of the Inner Hebrides, they abound in the great 
sheets and bosses of Tertiary volcanic rocks. These are the youngest formations 
through which they rise. But it is deserving of note, that they intersect every great 
group of these Tertiary volcanic products, so that they include in their number some 
of the latest known manifestations of eruptive action in the geological history of 
Britain. 

In the second place, in ranging across groups of rock belonging to such widely 
diverse periods, the dykes must necessarily often pass abruptly from one kind of material 
and geological structure to another. But, as a rule, they do so without any sensible 
deviation from their usual trend, or any alteration of their average width. Here and 
there, indeed, we may observe a dyke to follow a more wavy or more rapidly sinuous or 
zig-zag course in one group of rocks than in another. Yet, so far as I have myself 
been able to observe, such sinuosities may occur in almost any kind of material, 
and are not satisfactorily explicable by any difference of texture or arrangement 
in the rocks at the surface. No dyke traverses a greater variety of sedimentary forma- 
tions than that of Cleveland. In the eastern part of its course, it rises through all the 
Mesozoic beds up to the Cornbrash. Further west it cuts across each of the different 
subdivisions of the Carboniferous system ; and, of course, it must traverse all the older 
formations which underlie these. But the occasional rapid changes noticeable in its 
width and direction cannot be referred to any corresponding structure in the surrounding 
rocks. The Cheviot dyke crosses from the Carboniferous area of Northumberland into 
the Upper Silurian rocks and Lower Old Red Sandstone volcanic tract of the Cheviot Hills. 
It then strikes across the Upper Old Red Sandstone of Roxburghshire, and still maintain- 
ing the same persistent trend, sweeps westward into the Lower Silurian rocks of the 
Southern Uplands. Though liable to occasional deviations, these do not seem to have 
reference to any visible change of structure in the adjacent formations. Again, some of 
the great dykes at the head of Clydesdale furnish striking illustrations of entire 
indifference to the nature of the rock through which they run. Quitting the Lower 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 65 

Silurian uplands, they keep their line across Upper Silurian, Old Eed Sandstone and 
Carboniferous rocks, and through large masses of eruptive material. 

In the third place, not only are the dykes not deflected by great diversities in the 
lithological character of the rocks which they traverse, they even cross without deviation 
some of the most important geological features in the general framework of the country. 
Some of the Scottish examples are singularly impressive in this respect. Those which 
strike north-westward from the uplands of Clydesdale cross without deflection the great 
boundary -fault which, by a throw of several thousand feet, brings the Lower Old Red Sand- 
stone against the Lower Silurian rocks. They traverse some large faults in the valley of the 
Douglas coal-field, pass completely across the axis of the Haughshaw Hills, where the 
Upper Silurian rocks are once more brought up to the surface, and also the long felsite 
ridge of Priesthill. The dykes in the centre of the kingdom maintain their line across 
some of the large masses of igneous rock that protrude through the Carboniferous system. 
Further north, the dykes of Perthshire cut across the great sheets of volcanic material 
that form the Ochil Hills, as well as through the piles of sandstone and conglomerate of 
the Lower Old Eed Sandstone, and then go right across the boundary-fault of the 
Highlands, to pursue their way in the same independent manner through grit, quartzite, 
or mica-schist, and across glen and lake, moor and mountain. 

No one can contemplate these repeated examples of an entire waDt of connection 
between the dykes and the nature and arrangement of the rocks which they traverse 
without being convinced that the lines of vent up which the material of the dykes rose were 
not, as a rule, old fractures in the earth's crust, but were fresh fissures, opened across the 
course of the older dislocations and strike of the country by the same series of subterranean 
operations to which the uprise of the molten material of the dykes was also due. 

In the fourth place, the dykes for the most part are not coincident with lines of fault. 
After the examination of hundreds of dykes in all parts of the country, and with all the 
help which bare hill-sides and well-exposed coast sections can afford, I can almost reckon 
on my fingers the number of instances where dykes have availed themselves of lines of 
fault. Some of these will be immediately cited. To whatever cause we may ascribe the 
rupture of the solid crust of the earth, which allowed of the rise of molten rock to form the 
dykes, there can be no doubt that it was not generally attended with that displacement of 
level on one or both sides of the dislocation, which we associate with the idea of a fault. 
Nowhere can this important part of dyke-structure be more clearly illustrated than along 
the Cleveland dyke, where the igneous rock rises through almost horizontal Jurassic strata 
and gently inclined Coal Measures (figs. 7 and 8). Besides the localities already cited, 
mining operations both for coal and for the Liassic ironstone have proved over a wide 
area that the dyke has not risen along a line of fault. Again, in Skye, Eaasay, Eigg, and 
other parts of the west coast, where Jurassic strata and the horizontal basalts of the 
plateaux are plentifully cut through by dykes, the same beds may be seen on the same 
level on either side of them. 

In the fifth place, while complete indifference to geological structure is the general 



00 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

rule among the dykes, instances do occur in which the molten material has found its way 
upward along old lines of rupture. Most of such instances are to be found in districts 
where previously existing faults happened to run in the same general direction as that 
followed by the dykes. These lines of fracture would naturally be reopened by any great 
earth-movements acting in their direction, and would afford ready channels for the ascent 
of the lava. Yet it is curious that, even when their trend would have suited the line of 
the dykes, they have not been more largely made use of for the purpose of relief. Some 
of the best examples of the coincidence of dykes with pre-existing faults in the same 
direction are to be found in the Stirlingshire coal-field. The dyke that runs from 
Torphichen for 23 miles to Cadder occupies a line of fault which at Slamannan has a 
down-throw of more than 70 fathoms. The next dyke further south has also risen along 
an E. and W. fault. 

But other examples may be observed where pre-existing fissures have served to 
deflect dykes from their usual line of trend. Thus the Cleveland dyke, after crossing 
several faults in the Coal-Measures, at last encounters one near Cockfield Fell, which 
lies obliquely across its path. Instead of crossing this fault it bends sharply round a few 
points south of west, and after keeping along the southern flank of the fault for about 
a mile, sinks out of reach. Some of the Scottish examples are more remarkable. One of 
the best of them occurs in the Sanquhar coal-field, where a dyke runs for two miles and a 
half along the large fault that here brings down the Coal-Measures against the Lower 
Silurian rocks. At the north-western end of the basin, this fault makes an abrupt bend 
of 60° to W.S.W., and the dyke turns round with it, keeping this altered course for a mile 
and a half, when it strikes away from the fault, crosses a narrow belt of Lower Silurian 
rocks, and finds its way into the parallel boundary fault which defines the north-western 
margin of the Silurian rocks of the Southern Uplands. 

Some of the Perthshire dykes, where they reach the great boundary -fault of the 
Highlands, present specially interesting features. There can be no doubt that this 
dislocation is one of the most important in the general framework of the British Isles. 
We have not yet been able to ascertain definitely how much rock has been actually 
displaced by it. But the fact that in one place the beds of Old Red Sandstone are 
thrown on end for some two miles back from it, shows that it must be a very powerful 
fracture. Here, therefore, if anywhere, we might confidently anticipate either an entire 
cessation of the dykes, or at least a complete deflection of their course. It would require, 
we might suppose, a singularly potent dislocation to open a way for the ascent of the 
lava through such crushed and compressed rocks, and still more to prolong the general 
line of fracture on either side of the old fault. Two great dykes, about half a mile apart, 
run in a direction a little S. of W. across the plain of Strathcarn. Passing to the south 
of the village of Crieff, they hold on their way until they reach the highly-inclined beds 
of sandstone and conglomerate which here lean against the Highland fault in Glen Artney. 
They then turn round towards S.W., and run up the glen along the strike of the beds, 
keeping approximately parallel to the fault for about three miles, when they both strike. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



67 



across the fault, and pursue a W.S.W. line through the contorted crystalline rocks of the 
Highlands. About two miles south, another dyke continues its normal course across the 
belt of upturned Old Ked Sandstone ; but when it reaches the fault it bends round and 
follows the line of dislocation, sometimes coinciding with, sometimes crossing or running 
parallel with that line at a short distance (see fig. 12). 

Mr Clough has supplied me with notes of some remarkable examples recently observed 




Scale: one mck= one mile 



Fig. 17.— Map of the chief Basic Dykes between Lochs Riddon and Striven (C. T. Clough). The large E. and W. dyke 
is a continuation of that which reaches the shore of the Firth of Clyde at Dunoon. 



by him in eastern Argyleshire, where broad bands of basalt or other allied rock run in a 
N. and S. direction, and are formed by the confluence of N.W. and S.E. or N.N.W. and 
S. S.E. dykes, where they are drawn into a line of fault. These broad bands, he says, are 
not usually traceable for more than a mile or so, for the dykes of which they are made up 
will not be diverted from their regular paths for more than a certain distance, so that 
one by one the dykes leave the compound band to pursue their normal course. He adds, 
that the occasional great thickness of those compound bands depends partly on the size 



68 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

and partly on the number of separate dykes that are diverted into the line of transverse 
fissure ; for, where the fissure crosses an area with fewer N.W. dykes, the band becomes 
thinner or ceases altogether. 

In some rare cases, the dykes have been shifted by more recent faults. I shall have 
occasion to show that faults of several hundred feet have taken place since the Tertiary 
basalt-plateaux were formed. There is therefore no reason why here and there a fault 
with a low hade should not have shifted the outcrop of a dyke. But the fact remains 
that, as a general rule, the dykes run independently of faults even where they approach 
closely to them. Mr Clough has observed some interesting cases in south-eastern 
Argyleshire, where the apparent shifting of a dyke by faults proves to be deceptive, and 
where the dyke has for short distances merely availed itself of old lines of fracture. 
One of the most remarkable of these is presented by the large dyke which runs westward 
from Dunoon. No fewer than three times, in the course of four miles between Lochs 
Striven and Riddon, Mr Clough has found this dyke to make sharp changes of trend 
nearly at right angles to its usual direction, where it encounters N. and S. faults (fig. 
17). It would be natural to conclude that these changes are actual dislocations due to 
the faults. But this careful observer has been able to trace the dyke in a very attenuated 
and uncrushed form along some of these cross faults, and thus to prove that the faults 
are of older date, but that they have modified the line of the long E. and W. fissure up 
which the material of the dyke ascended. 

§ 17. Data for Estimating the Geological Age of the Dykes. 

I have already assigned reasons for regarding the system of E. and W. or S.E. and 
N.W. dykes as belonging to the Tertiary volcanic period in the geological history of the 
British Islands. But I have no evidence that they were restricted to any part of that 
period. On the contrary, there is every reason to consider the uprise of the earliest 
and latest dykes to have been separated by a protracted interval. That they do not 
all belong to one epoch I shall now proceed to prove. 

The intersection of one dyke by another furnishes an obvious criterion of relative age. 
Macculloch drew attention to this test, and stated that it had enabled him to make out 
two distinct sets of dykes in Skye and Rum. But he confessed that it failed to afford any 
information as to the length of the interval of time between them.* It is not always so 
easy as might be thought to make sure which of two intersecting dykes is the older. 
We have to look for the finer-grained marginal strip at the edge of a dyke, which, where 
traceable across another dyke, marks at once their relative age. The cross joints of the 
two dykes also run in different directions. It is obvious that in the case of two such 
dykes, no longer interval need have elapsed between their successive production than was 
needed for the solidification and assumption of a joint-structure by the older one before the 
younger broke through it. They may both belong to one brief period of volcanic activity. 
But when we pass to a series of dykes traversing a considerable district of country, and 

* Trans. Geol. Soc, iii. p. 75. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 

find that those which run in one direction are invariably cut by those which run in 
another, the inference can hardly be resisted that they do not belong to the same eruption, 
but mark successive epochs of volcanic energy. An excellent example of this kind of 
evidence is furnished by Mr Clough from eastern Argyleshire. The east and west dykes in 
that district are undoubtedly older than those which run in a N.N.W. direction (fig. 17). 
The latter are by far the most abundant, and are on the whole much narrower, less per- 
sistent, and finer in grain. On the opposite coast of the Clyde, a similar double set of 
dykes may be traced through Renfrewshire, those in an east and west direction being com- 
paratively few, while the younger N.N.W. series is well developed. The great sheets or 
" sills" connected with one of the Stirlingshire dykes, already described, appear to me to 
furnish similar evidence in the younger- dykes which run through them. And this 
evidence is peculiarly valuable, for it shows a succession even among adjacent dykes 
which all run in the same general direction. 

But in all these cases it is obvious that we have little indication of the length of time 
that intervened between the successive uprise of the dykes. In Skye, however, we meet 
with more definite evidence that the interval must have been in some cases a protracted 
one. In a paper published as far back as the year 1857,* I showed that the basic dykes 
of Strath in Skye were of two ages ; that one set had been erupted before the appearance 
of the so-called " syenite " of that district, and was cut off by the latter rock ; and that 
the other had arisen after the ** syenite " which it intersected. Recent re-examination 
has enabled me to confirm and extend this observation. The granitoid eruptions of the 
Inner Hebrides are marked by so varied a series of rocks, and so complex a geological 
structure, that they may, with some confidence, be regarded as having occupied a 
considerable interval of geological time. Yet we find that this episode in the volcanic 
history was both preceded and followed by the extravasation of basic dykes. I have been 
unable to make out any appreciable petrographical difference between the two sets of 
dykes. But for the evidence of the granophyre, they would unquestionably be all classed 
together as one series. 

Let me add one further piece of evidence to prove that some of the dykes go back to 
a remote part of the volcanic history of Tertiary time in Britain. The Scuir of Eigg, to 
which fuller reference will be made in a later part of this memoir, is formed of a mass 
of pitchstone, which has filled up an ancient valley eroded out of the terraced basalts of 
the plateaux. At both ends of the ridge, these basalts are seen to be traversed by dykes 
that are abruptly cut off by the shingle of the old river-bed which the pitchstone has 
occupied (fig. 63). It is thus evident that, though these dykes are younger than the 
plateau-basalts, they are much older than the excavation of the valley out of these basalts, 
and still older than the eruption of pitchstone. The latter rock probably belongs to the 
close of the period of acid eruptions just referred to, and we have seen that abundant 
dykes were extruded after most of the acid rocks had appeared. 

It is certain, therefore, that the dykes which in Britain form part of the great Tertiary 

* Quart. Jour. Geol. Soc, xiv. p. 1. 
VOL. XXXV. PART 2. K 



70 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

volcanic series, were not all produced at one epoch, but belong to at least two (and 
possibly to many more) episodes in one long volcanic history. As they rise through 
every member of that series of rocks (save the pitchstones), some of them must be among 
the very latest records of the prolonged volcanic activity. But, on the other hand, 
some may go back to the beginning of the Tertiary volcanic period. 

§ 18. Origin and History of the Dykes. 

Reference has already been made to the doubt expressed by Macculloch whether 
the dykes of Skye had been filled in from above or from below. That the dykes of 
the country as a whole were supplied from above, was the view entertained and 
enforced by Boue. He introduces the subject with the following remarks : — " Scot- 
land is renowned for the number of its basaltic veins, which gave Hutton his ideas 
regarding the injection of lava from below; but, as the greatest genius is not 
infallible, and as volcanic countries present us with examples of such veins arising 
evidently from accidental fissures that were filled up by currents of lava which moved 
over them, and as the Scottish instances are of the same kind, we regard it as infinitely 
probable that all these veins have been formed in the same way, notwithstanding the 
enormous denudation which this supposition involves ; and that only rarely do cases 
occur where they have been filled laterally or in some other irregular manner." # I need 
not say that this view, which, except among Wernerians, had never many supporters, 
has long ago been abandoned and forgotten. There is no longer any question that the 
molten material came from below. 

1. In discussing the history of the dykes, we are first confronted with the problem of 
the formation of the fissures up which the molten material rose. From what has been 
said above regarding the usual want of relation between dykes and the nature and 
arrangement of the rocks which they traverse, it is, I think, manifest that the fissures 
could not have been caused by any superficial action, such as that which produces cracks 
of the ground during earthquake-shocks. The fact that they traverse rocks of the most 
extreme diversities of elasticity, structure, and resistance, and yet maintain the same 
persistent trend through them all, shows that they originated far below the limits to 
which the known rocks of the surface descend. We have seen that in the case of the 
Cleveland dyke, the fissure can be proved to be at least some three miles deep. But the 
seat of origin of the rents no doubt lay much deeper down within the earth's crust. 

It is also evident that the cause which gave rise to these abundant fissures must have 
been quite distinct from the movements that produced the prevalent strike and the main 
faults of this country. From early geological time, as is well known, the movements of 
the earth's crust, beneath the area of Britain, have been directed in such a manner as to 
give the different stratified formations a general north-east and south-west strike, and 
to dislocate them by great faults with the same average trend. But the fissures of the 
Tertiary dykes run obliquely and even at a right angle across this prevalent older series 

* Essai Geologique sur I'Ecosse, p. 272. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 71 

of lines, and are distinct from any other architectonic feature in the geology of the 
country. They did not arise therefore by a mere renewal of some previous order of 
disturbances, but were brought about by a new set of movements to which it is 
difficult to find any parallel in the earlier records of the region.* 

We have further to remember that the fissures were not produced merely by one great 
disturbance. The evidence of the dykes proves beyond question that some of them are 
earlier than others, and hence that the cause to which the fissures owed their origin came 
into operation more than once during the protracted Tertiary volcanic period. One of 
the most instructive lessons in this respect is furnished by the huge eruptive masses of 
gabbro and granitoid rocks in Skye. These materials have been erupted through the 
plateau-basalts. The granitoid bosses are the younger protrusions, for they send veins 
into the gabbros ; but their appearance was later than that of some of the dykes and 
older than that of others. Nevertheless, the latest dykes maintain the usual north-westerly 
trend across the thickest masses both of the gabbro and the granophyre. Thus we learn 
that, even after the extrusion of thousands of feet of such solid crystalline igneous rocks, 
covering areas of many square miles, the Assuring of the ground was renewed, and rents 
were opened through these new piles of material. From the evidence of the dykes also, 
we learn that the general direction of the fissures remained from first to last tolerably 
uniform. Here and there indeed, where one set of dykes traverses another, as in the 
basin of the Clyde, we meet with proofs of a deviation from the normal trend. But it is 
remarkable that the very youngest dykes which pierce the eruptive bosses of the Inner 
Hebrides rose in fissures that were opened in the normal north-westerly line through 
these great protrusions of basic and acid rock. 

Such a gigantic system of parallel fissures points to great horizontal tension of the 
terrestrial crust over the area in which they were developed. Hopkins, many years ago, 
discussed from the mathematical side the cause of the production of such fissures.t He 
assumed the existence of some elevatory force acting under considerable areas of the 
earth's crust at any assignable depth, either with uniform intensity at every point, or with 
a somewhat greater intensity at particular points. He did not assign to this force any 
definite origin, but supposed it "to act upon the lower surface of the uplifted mass 
through the medium of some fluid, which may be conceived to be an elastic vapour, or, 
in other cases, a mass of matter in a state of fusion from heat." J He showed that such 
an upheaving force would produce in the affected territory a system of parallel longi- 
tudinal fissures, which, when not far distant from each other, could only have been 
formed simultaneously, and not successively ; that each fissure would begin not at the 
surface, but at some depth below it, and would be propagated with great velocity ; that 
there would be more fissures at greater than at lesser depths, many of them never reaching 
the surface ; that they would be of approximately uniform width, the mean width tending 

* The only other known example of such a dyke-structure is that of the Pre-Cambrian series of dykes in the 
Archaean gneiss of Sutherland. 

t Cambridge Phil. Trans., vi. (1835) p. 1. % Op. cit, p. 10. 



72 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

to increase downwards ; that continued elevation might increase these fissures, but that 
new fissures in the same direction would not arise in the separated blocks which would 
now be more or less independent of each other; that subsequent subsidences would give 
rise to transverse fissures, and by allowing the separated blocks to settle down would 
cause irregularities in the width of the great parallel fissures. He considered also the 
problem presented by those cases where the ruptures of the terrestrial crust have been 
filled with igneous matter, and now appear as dykes. " The results above obtained," he 
says, "will manifestly hold equally, whether we suppose the uplifted mass acted upon 
immediately through the medium of an elastic vapour or by matter in a state of fusion in 
immediate contact with its lower surface. In the latter case, however, this fused matter 
will necessarily ascend into the fissures, and if maintained there till it cools and solidifies, 
will present such phenomena as we now recognise in dykes and veins of trap." * 

The existence of a vast lake or reservoir of molten rock under the fissure-region of 
Britain is demonstrated by the dykes. But, if we inquire further what terrestrial opera- 
tion led to the uprise of so vast a body of lava towards the surface in older Tertiary time, 
we find that as yet no satisfactory answer can be given. 

2. The rise of molten rock in thousands of fissures over so wide a region is to my 
mind by far the most wonderful feature in the history of volcanic action in Britain. The 
great plateaux of basalt, and the mountainous bosses of rock by which they have been 
disrupted, are undoubtedly the most obvious memorials of Tertiary volcanism. But, 
after all, they are merely fragments restricted to limited districts. The dykes, however, 
reveal to us the extraordinary fact that, at a period so recent as older Tertiary time, 
there lay underneath the area of Britain a reservoir or series of reservoirs of lava, the 
united extent of which must have exceeded 40,000 square miles. 

That the material of the dykes rose in general directly from below, and was not 
injected laterally along the open fissures, cannot be doubted. The narrowness of these 
rents, and their enormous relative length, make it physically impossible that molten rock 
could have moved along k them for more than a short distance. The homogeneous 
character of the rock, the remarkable scarcity of any broken-up consolidated fragments 
of it immersed in a matrix of different grain, the general uniformity of composition and 
structure from one end of a long dyke to another, the spherical form of the amygdules, 
the usual paucity of fragments from the fissure walls — all point to a quiet welling of the 
lava upward. Over the whole of the region traversed by the dykes, from the hills of 
Yorkshire and Lancashire to the remotest Hebrides, molten rock must have lain at a 
depth, which, in one case, we know to have exceeded three miles, and which was probably 
everywhere considerably greater than that limit. 

Forced upwards, partly perhaps by pressure due to. terrestrial contraction and partly 
by the enormous expansive force of the gases and vapours absorbed within it, the lava 
rose in the thousands of fissures that had been opened for it in the solid overlying crust. 
That in most cases its ascent terminated short of the surface of the ground may reasonably 

* Op. cit., p. 69. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 73 

be inferred. At least, we know, that many dykes do not reach the present surface, and 
that those which do have shared in the enormous denudation of the surrounding country. 
That even in the same dyke the lava rose hundreds of feet higher in one place than at 
another is abundantly proved. When, however, we consider the vast number of dykes 
that now come to the light of day, and reflect that the visible portions of some of them 
differ more than 3000 feet from each other in altitude, we can hardly escape the conviction 
that it would be incredible that nowhere should the lava have flowed out at the surface. 
Subsequent denudation has undoubtedly removed a great thickness of rock from what 
was the surface of the ground during older Tertiary time, and hundreds of dykes are now 
exposed that originally lay deeply buried beneath the overlying part of the earth's 
crust through which they failed to rise. But some relics, at least, of the outflow of lava 
might be expected to have survived. I believe that such relics remain to us in the great 
basalt-plateaux of Antrim and the Inner Hebrides. These deep piles of almost horizontal 
sheets of basalt, emanating from no great central volcanoes, but with evidence of many 
small local vents, appear to me to have proceeded from dykes that reached the highest 
level, and from which orifices, communicating with the surface of the ground, allowed the 
molten material to flow out in successive streams with occasional accompaniments of 
fragmentary ejections. The structure of the basalt-plateaux, and their mode of origin, 
will form the subject of the next division of this paper. . 

We can hardly suppose, however, that the lava flowed out only in the western region 
of the plateaux. Probably it was most frequently emitted and accumulated to the 
greatest depth in that area. But over the centre of Scotland and north of England there 
may well have been many places where dykes actually communicated with the outer air, 
and allowed their molten material to stream out over the surrounding country. The 
disappearance of such outflows need cause no surprise, when we consider the extent of the 
denudation which many dykes demonstrate. I have elsewhere shown that all over Scot- 
land there is abundant proof that hundreds and even thousands of feet of rock have been 
removed from parts of the surface of the land since the time of the uprise of the dykes.* 
The evidence of this denudation is singularly striking in such districts as that of Loch 
Lomond, where the difference of level between the outcrop of the dykes on the crest of 
the ridges and in the bottom of the valley exceeds 3000 feet. It is quite obvious that, 
had the deep hollow of Loch Lomond lain as it now does in the pathway of these dykes, 
the molten rock, instead of ascending to the summits of the hills, would have burst out 
on the floor of the valley. We are, therefore, forced to admit that a deep glen and lake- 
basin have been in great measure hollowed out since the time of the dyke. If a depth of 
many hundreds of feet of hard crystalline schists could have been removed in the interval 
there need be no difficulty in understanding that by the same process of waste, many 
sheets of solid basalt have been gradually stripped off the face of central Scotland and 
northern England. 

* Scenery of Scotland, 2d edit. (1887), p. 149. But see the remarks already made (p. 55) on the curious coincidence 
sometimes observable between the upper limit of a dyke and the overlying inequalities of surface. 



74 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

This association of dykes with the out-welling of lava and with the accumulation of deep 
and extensive volcanic plateaux, is paralleled in other parts of the world. The description 
by Mr G. T. Clark of the dykes connected with the vast basaltic sheets of the Bombay 
Presidency corresponds almost exactly with that which I have given of those of this 
country. The Indian, like the British, examples occur in great numbers, rising through 
every rock in the district up to the crests of the Ghauts, 4000 feet above the sea. They 
vary from one or two to 10, 20, 40, and even occasionally 100 or 150 feet in width, 
and are often many miles in length. They observe a general parallelism in one average 
direction, and show no perceptible difference in character even when traced up to elevations 
of 3000 and 4000 feet* 

To this and other areas, where horizontal sheets of basalt cover enormous tracts of 
country with no great central volcanic cones from which the material could have come, 
fuller reference will be made in the next division of this paper, which treats of the basalt- 
plateaux of the British Islands.t 



II. THE VOLCANIC PLATEAUX. 

We have now to consider the structure and history of those volcanic masses which, 
during Tertiary time, were ejected to the surface within the area of the British Islands, 
and now remain as extensive basalt-plateaux. Short though the interval has been in a 
geological sense since these rocks were erupted, it has been long enough to allow of very 
considerable movements of the ground and of enormous denudation. Hence the 
superficial records of Tertiary volcanic action have been reduced to a series of broken and 
isolated fragments. I have already stated that no evidence now remains to show to what 
extent there were actual superficial outbursts of volcanic material over the rest of the 
dyke-region of Britain, and the subsequent waste of the surface has been so enormous 
that various lava-fields may quite possibly have stretched across parts of England and 
Scotland, from which they have since been wholly stripped off, leaving behind them only 
that wonderful system of dykes from which their molten materials were supplied. 

There can be little doubt, however, that whether or not other Phlegrean fields 
extended over portions of the country whence they have since been worn away, the chief 
volcanic tract lay to the west in a broad and long depression that stretched from the 
south of Antrim to the Minch. From the southern to the northern limit of the 
fragmentary lava-fields that remain in this depression is a distance of some 250 miles, 
and the average breadth of ground within which these lava-fields are preserved may be 
taken to range from 20 to 50 miles. If, therefore, the sheets of basalt and layers of tuff 

* Quart. Jour. Geol. Soc, xxv. (1869) p. 163. 

t It is interesting to note that in the great paper on Physical Geology already cited, Hopkins considered the question 
of the outflow of lava from the fissures which he discussed. " If the quantity of fluid matter forced into these fissures," 
he says, " be more than they can contain, it will, of course, he ejected over the surface; and if this ejection take place 
from a considerable number of fissures, and over a tolerably even surface, it is easy to conceive the formation of a bed 
of the ejected matter of moderate and tolerably uniform thickness, and of any extent" (op. cit., p. 71). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 75 

extended over the whole of this strip of country, they covered a space of some 7000 or 
8000 square miles. But they were not confined to the area of the British Islands. 
Similar rocks rise into plateaux in the Faroe Islands, and it may reasonably be conjectured 
that the remarkable submarine ridge which extends thence to the north-west of Scotland, 
and separates the basin of the Atlantic from that of the Arctic Ocean, is partly at least 
of volcanic origin. And still further north come the extensive Tertiary basaltic plateaux 
of Iceland, while others of like aspect and age cover a vast area in southern Greenland. 
Without contending that one continuous belt of lava-streams stretched from Ireland to 
Iceland and Greenland, we can have no doubt that in older Tertiary time the north-west 
of Europe was the scene of more widely- extended volcanic activity than showed itself at 
any other period in the geological history of the whole continent. Possibly, as I have 
already suggested, the present active vents of Iceland and Jan Mayen are the descendants 
in uninterrupted succession of those that supplied the materials of the Tertiary basaltic 
plateaux, the volcanic fires slowly dying out from south to north. But so continuous and 
stupendous has been the work of denudation in these northern regions, where winds and 
waves, rain and frost, floe-ice and glaciers reach their highest level of energy, that the 
present extensive sheets of igneous rock can be regarded only as magnificent relics, the 
grandeur of which furnishes some measure of that which characterised the last episode in 
the extended volcanic records of Britain. 

The long and wide western valley in which the basalt-plateaux of this country were 
accumulated seems, from a remote antiquity, to have been a theatre of considerable 
geological activity. There are traces of some such valley or depression even back in the 
period of the Torridon sandstone of the north-west which was laid down in it between the 
great ridge of the Outer Hebrides and some other land to the east. The Lower Old Red 
Sandstone of Lome may represent the site of one of its lakes. The Carboniferous rocks, 
which run through the north of Ireland, cross into Cantyre, and are found even as far 
north as the Sound of Mull, mark how, in later Palaeozoic time, the same strip of country 
was a region of subsidence and sedimentation. During the Mesozoic ages, similar 
operations were continued ; the hollow sank several thousand feet, and Jurassic strata to 
that depth filled it up. Before the Cretaceous period, underground movements had 
disrupted and irregularly upheaved the Jurassic deposits, and prolonged denudation had 
worn them away, so that when the Cretaceous formations came to be laid down on the 
once more subsiding depression, they were spread out with a strong unconformability on 
everything older than themselves, resting on many successive horizons of the Jurassic 
system, and passing from these over to the submerged hill-sides of the crystalline schists. 
Yet again, after the accumulation of the Chalk, the sea-floor along the same line was 
ridged up into land, and the Chalk, exposed to denudation, was deeply trenched by valleys, 
and entirely removed from wide tracts which it once covered. 

It was in this long broad hollow, with its memorials of repeated subsidences and 
upheavals, sedimentation and denudation, that the vigour of subterranean energy at last 
showed itself in volcanic outbreaks, and in the gradual piling up of the materials of the 



76 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

basalt-plateaux. So far as we know, these outbursts were subserial. At least no trace 
of any marine deposit has yet been found even at the base of the pile of volcanic rocks. 
Sheet after sheet of lava was poured out, until several thousand feet had accumulated, 
so as perhaps to fill up the whole depression, and once more to change entirely the aspect 
of the region. But the Volcanic period, long and important as it was in the geological 
history of the country, came to an end. It too was merely an episode during which 
denudation still continued active, and since which subterranean disturbance and superficial 
erosion have again transformed the topography. In wandering over these ancient lava- 
fields, we see on every hand the most stupendous evidence of change. They have been 
dislocated by faults, sometimes with a displacement of hundreds of feet, and have been 
hollowed out into deep and wide valleys and arms of the sea. Their piles of solid rock, 
thousands of feet thick, have been totally stripped off from wide tracts of ground which 
were once undoubtedly buried under them. Hence, late though the volcanic events are 
in the history of the land, they are already separated from us by so vast an interval that 
there has been time for cutting down the wide plateaux of basalt into a series of mere 
scattered fragments. But the process of land-sculpture has been of the utmost service to 
geology, for, by laying bare the inner structure of these plateaux, it has provided 
materials of almost unequalled value and extent for the study of one type of volcanic 
action. 

§ 1. Petrography. 

The superficial outbursts of volcanic action during Tertiary time in Britain are 
represented by a comparatively small variety of rocks. By far the largest area and 
thickest mass consist of dark basic lavas. In only one locality (Isle of Eigg) has any 
outflow of acid lava been detected. Between the lava-sheets occasional layers of volcanic 
and even non-volcanic fragmental rocks occur. The general lithological characters of 
the whole group of plateau-rocks may here be briefly enumerated. 

1. Lavas. — In external characters these rocks range from coarsely crystalline varieties, 
in which the constituent minerals may be more or less readily detected with the naked eye 
or a field-lens, to dense black compounds in which only a few porphyritic crystals may 
be microscopically visible. They are easily recognised as pertaining in the vast majority 
of cases to the great group of the dolerites and basalts. One of their characteristic 
features is the presence of the ophitic structure, sometimes only feebly developed, some- 
times showing itself in great perfection. Many of the rocks are holo-crystalline, but 
usually show more or less interstitial matter (dolerites) ; in others the texture is finer, 
and the interstitial matter more developed (basalts) ; in no case, so far as I have observed, 
are there any glassy varieties, which are restricted to the dykes, though in some of the 
basalts there is a considerable proportion of glassy or incompletely devitrified substance. 
The felspars are of the characteristic lath-shaped forms, and are usually quite clear and 
fresh. The augite resembles that of the dykes, occurring sometimes in large plates that 
enclose the felspars, at other times in a finely granular form. Olivine is frequently not 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 77 

to be detected, even by green alteration products. Magnetite is sometimes present in 
such quantity as to affect the compass of the field-geologist. Porphyritic varieties 
occur with larger crystals of a different form from the laths of the base ; but such 
varieties are, I think, less frequent among the plateau-rocks than among the dykes. 

In a few localities, there are found intercalated with the ordinary dark heavy 
dolerites and basalts certain pale rocks of much lower specific gravity (2 7 1-2 7 4). 
Externally these sheets are dull in texture, sometimes strongly amygdaloidal, sometimes 
with a remarkable platy structure, which, in the process of weathering, causes them to 
split up like stratified rocks. Examined with the microscope, they are found to consist 
almost wholly of felspar in minute laths or microliths, but in none of my specimens 
sufficiently definite for satisfactory determination. In one of the best slides Dr F. 
Hatch, in whose hands I placed it, finds that " each lath of this abnormal felspar passes 
imperceptibly into those adjacent to it ; the double refraction being very weak, and the 
twin-striation, if present, not being traceable." He suggests whether the rock " originally 
consolidated as a glass, poor in iron and magnesia, the development of the felspar being 
due to devitrification." * Some of the varieties are amygdaloidal, the cells being filled 
with epidote, which also appears in the fissures, and sometimes even as a constituent of 
the rock. To such compounds I do not know that any existing petrographical name is 
applicable. As they form the upper portion of Ben More, and the tops of some of its 
neighbours in Mull, I have been in the habit of speaking of them as the " felspathic 
lavas "or " pale-group " of Ben More, and it will be preferable to use some such vague 
definition until their true chemical and mineralogical characters have been worked out. 

Passing now to the occurrence of the lavas as beds of rock in the plateaux, we find 
them to present three well-marked types, all of which, however, pass into each other. 
1st, Massive and amorphous ; 2d, Prismatic ; 3d, Amygdaloidal and slaggy. 

1. The more coarsely crystalline varieties (dolerites) are apt to occur in thick massive 
beds, with no definite structure except the usual somewhat irregular joints placed 
perpendicularly to the upper and under surfaces. In their general aspect, such beds 
cannot readily be separated from intrusive sheets. But where they are not intrusive, 
they will generally be found somewhat cellular towards their upper and lower surfaces ; 
while, where intrusive, they are generally more close-grained there than anywhere else. 
Rocks of this character are less frequent than those of the other two varieties. 

2. Prismatic structures are typical of the more compact heavy basalts. A considerable 
variety is observable in the degree of perfection of their development. Where they are 

* In the course of my investigations I have had many hundreds of thin slices cut from the Tertiary volcanic rocks 
for microscopic determination. These I have myself studied in so far as their microscopic structure appeared likely to 
aid in the investigation of those larger questions of geological structure in which I was more specially interested. But 
for their detailed examination I have placed them with Dr Hatch, in whose hands, together with the large series of 
specimens accumulated by the Geological Survey, they will form the subject of a future memoir on the microscopic 
petrography of this most interesting group of rocks. He has submitted to me the results of his preliminary examina- 
tion, and where these offered points of geological import I have availed myself of them by citations in the course of 
this memoir. Professor Judd, in a series of valuable papers, has discussed the general petrography of the Tertiary 
volcanic rocks ; Quart. Jour. Geog. Soc, vols, xxxix., xli., xlii. 

VOL. XXXV. PART 2. L 



78 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

least definite, the rock is traversed by vertical joints, somewhat more regular and close- 
set than those in the dolerites, by the intersection of which it is separated into rude 
quadrangular or polygonal columns. The true prismatic structure is shown in two chief 
forms, (a) The rock is divided into close-fitting parallel, usually six-sided, columns ; 
the number of sides varying, however, from three up to nine. The columns run the 
whole thickness of the bed, and vary thus from 8 or 10 to 40 or even 80 feet in length. 
They are segmented by cross joints which sometimes, as at the Giant's Causeway, take 
the ball and socket form. Occasionally they are curved, as at the well-known Clam-shell 
cave of Stafla. (b) The prisms are much smaller, and diverge in wavy groups crowded 
confusedly over each other, but with a general tendency upwards. This starch-like 
aggregation may be observed superposed directly upon the more regular columnar form, 
as at the Giant's Causeway and also at Stafla. 

3. It may often be noticed that, even where the basalt is most perfectly prismatic, it 
presents a cellular and even slaggy structure at the bottom. The rock that forms the 
Giant's Causeway, for instance, is distinctly vesicular, the vesicles being drawn out in a 
general E. and W. direction. The beautifully columnar bed of Stafla is likewise slaggy 
and amygdaloidal for a foot or so upwards from its base, and portions of this lower layer 
have here and there been caught up and involved in the more compact material above 
it. Even the bottom of the confusedly prismatic bed above the columnar one on that 
island also presents a cellular texture. A similar rock at Ardtun, in Mull, passes 
upward into a rugged slag and confused mass of basalt blocks, over which the leaf-beds 
lie. At Loch-na-Mna, in the island of Eigg, one of the basalts presents in places a 
remarkable streaky structure, due, doubtless, to the arrangement of its component 
materials during the flow of the still molten rock. 

Amygdaloidal structure is more or less well developed throughout the whole series 
of basalts. But it is especially marked in certain abundant sheets, which, for the sake of 
distinction, are called amygdaloids. These beds, which form a considerable proportion of 
the materials of every one of the plateaux, are distinguished by the abundance and large 
size of their vesicles. In some places, these cavities occupy at least as much of the 
rock as the solid matrix in which they lie. They have generally been filled up with 
some infiltrated mineral — calcite, chalcedony, zeolites, &c. The amygdules of the west of 
Skye and of Antrim have long been noted for their zeolitic enclosures. As a consequence 
of their cellular texture and the action of infiltrating water upon them, these amygdaloidal 
beds are always more or less decomposed. Their dull, lumpy, amorphous beds contrast 
well with the prismatic sheets above and below them, and as they crumble down they 
are apt to be covered over with vegetation. Hence, on a sea-cliff or escarpment, the green 
declivities between the prominent columnar basalts usually mark the place of these 
less durable bands. 

Exceedingly slag-like lavas are to be seen among the amygdaloids, immediately 
preceded and followed by beds of compact black basalt with few or no vesicles. From 
the manner in which such rocks yield to the weather, they often assume a singularly 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 79 

deceptive resemblance to agglomerates. One of the best examples of this resemblance 
which have come under my notice is that of the rock on which stands Dunluce Castle, on 
the north coast of Antrim. Huge rounded blocks of a harder consistency than the rest 
of the rock project from the surface of the cliffs, like the bombs of a true volcanic 
agglomerate, while the matrix in which they are wrapped has decayed from around them. 
But an examination of this matrix will soon convince the observer that it is strongly 
amygdaloidal, and that the apparent " bombs " are only harder and less cellular portions 
of it. The contrast between the weathering of the two parts of the rock seems to have 
arisen from an original variety in the relative abundance of steam-cavities. Another 
singular instance occurs at the foot of the outlier of Fionn Chro (fig. 51), in the island of 
Rum. A conspicuous band underlying the basalts there might readily be taken for a 
basalt-conglomerate. But in this case, also, the apparent matrix is found to be 
amygdaloidal, and the rounded blocks are really amygdules, sometimes a foot in length, 
filled or lined with quartz, chalcedony, &c. 

A somewhat different structure, in which, however, the appearance of volcanic breccia 
or agglomerate due to explosion from a vent is simulated, may be alluded to here. The 
best instance which I have observed of it occurs at the south end of Loch-na-Mna, in the 
island of Eigg. The basalt above referred to as occurring at this locality shows on its 
weathered surfaces a remarkable streaky structure that gives rise to prominent thin nearly 
parallel ribs coincident with the direction of bedding. This arrangement, probably due, 
as I have said, to the flow of the basalt while still unconsolidated, can hardly be traced 
with the naked eye on a fresh fracture of the rock, the whole appearing as a black 
compact basalt. On the weathered faces, the streaky layers may be observed to have 
been broken up, and their disconnected fragments have been involved in ordinary basalt 
wherein this flow-structure is not developed, while large blocks and irregular masses are 
wrapped round in a more decomposing matrix. There can be no doubt that in such 
cases we see the effects of the disruption of chilled crusts, and the entanglement of the 
broken pieces in the still fluid lava. 

Great variety is to be found in the thickness of different sheets of lava in the plateaux. 
Some of them are not more than 6 or 8 feet ; others reach to 80 or 100 feet, and some- 
times, though rarely, to even greater dimensions. In Antrim, the average thickness of 
the flows is probably from 15 to 20 feet.* In the fine coast-sections at the Giant's 
Causeway, however, some bands may be seen far in excess of that measurement. The 
bed that forms the Causeway, for instance, is about 60 or 70 feet thick, and seems to 
become even thicker further east. Along the great escarpment, 700 feet high, which 
rises from the shores of Gribon, on the west coast of Mull, there are twenty separate beds, 
which gives an average of 35 feet for the thickness of each flow. On the great range of 
sea-precipices, on the west coast of Skye, which present the most stupendous section of 
the basalts anywhere to be seen within the limits of the British Islands, the average 
thickness of the beds can be conveniently measured. At the Talisker cliffs some of the 

* See Explanation of Sheet 20, Geol. Survey, Ireland, p. 11. 



80 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



flows are not more than 6 or 8 feet ; others are 30 or 40 feet. In the vast walls that 
form the seaward margin of the tableland of Macleod's Tables (fig. 21), fourteen successive 
beds of basalt can be counted in a vertical section of 400 feet, which is equal to an 
average thickuess of about 28 feet. But some of the basalts are only about 6 feet thick, 
while others are 50 or 60. 

Each bed appears, on a cursory inspection, to retain its average thickness, and to be 
continuous for a long distance. But I believe that this persistence is in great measure 
deceptive. It is not often that we can follow the same bed with absolutely unbroken 
continuity for more than a mile or two. Even in the most favourable conditions, such 
as are afforded by a bare sea-cliff on which every bed can be seen, there occur small 
faults, gullies where the rocks are for the time concealed, slopes of debris, and other 
failures of continuity ; while the rocks are generally so like each other, that on the further 
side of any such interruption, it is not always possible to make sure that we are still 
tracing the same bed of basalt which we may have been previously following. On the 
other hand, a careful examination of one of these great natural sections will usually 
supply us with proofs that, while the bedded character may continue well marked, the 




< I ; ■' ' ' ; ' 5 : j i ( 

Fig. 18. — Termination of Basalt-beds, Carsaig, Mull. 



individual beds die out, and are replaced by others of similar character. On the south 
coast of Mull, for instance, cases may be observed where the basalt of one sheet abruptly 
wedges out, and is replaced by that of another. Where both are of the same variety of 
rock, it requires close inspection to make out the difference between them ; but where 
one is a green, dull, earthy, amorphous amygdaloid, and the other is a compact, black, 
prismatic basalt, the contrast between the two beds can be recognised from a distance 
(fig. 18). Again, along the west coast of Skye, the really lenticular character of the 
beds can be well seen. 

In Antrim also, where similar proofs may be obtained, remarkable evidence is 
presented of the rapid attenuation not of single beds only, but of a whole series of basalts. 
Thus, at Ballycastle, the group of lavas known as the Lower Basalts, which underlie the 
well-known horizon of iron-ore, are at least 350 feet thick. But, as we trace them west- 
wards, bed after bed thins out until, a little to the west of Ballintoy, a distance of only 
about 6 miles, the whole depth of the group has diminished to somewhere about 40 feet. 
A decrease of more than 300 feet in six miles or 50 feet per mile points to considerable 



DURING THE TEETIAEY PERIOD IN THE BRITISH ISLES. 81 

inequalities in the accumulation of the lavas. If the next series of flows came from 
another vent and accumulated against such a gentle slope, it would be marked by a slight 
unconformability. Structures of this kind are much rarer than we should expect them 
to be, considering the great extent to which the plateaux have been dissected and laid 
open in cliff sections. Near the west end of Glen More, in Mull, I observed a hillside 
where, as seen from a little distance, one series of basalts appears to be banked up against 
the edges of another. 

A common feature in all the plateaux is the intervention of a red layer between 
successive sheets of basalt. These red streaks form a striking feature on many sea-cliffs, 
and emphasise the bedded character of the volcanic series. Examined more closely, the 
thin red line is found to be a layer of clay or bole which shades into the decomposed top 
of the bed whereon it lies, and is usually somewhat sharply marked off from that which 
covers it. This layer has long, and I think correctly, been regarded as due to the 
atmospheric disintegration of the surface of the basalt on which it occurs, before the 
eruption of the overlying flow. It varies in thickness from a mere line up to a foot or 
more, and it passes into the tuffs and clays which are sometimes interposed between the 
sheets of basalt. 

2. Fragmented Rocks. — While the plateaux are built up mainly of successive flows 
of basaltic lavas, they include various intercalations of fragmental materials, which, though 
of trifling thickness, are of great interest and importance in regard to the light which 
they cast on the history of the different regions during the volcanic period. I shall 
enumerate the chief varieties of these rocks here, and give fuller details regarding their 
stratigraphical relations and mode of occurrence in connection with the succession of beds 
in each of the plateaux. 

a. Volcanic Agglomerates. — Under this name are included all the tumultuous 
unstratified masses of fragmentary materials which fill eruptive vents in and around the 
plateaux. The stones vary in size up to blocks several feet in diameter. They consist 
for the most part of basalts, often highly slaggy and scoriaceous, also fragments of 
different acid eruptive rocks (generally felsitic in texture), with pieces of the non-volcanic 
rocks through which the volcanic pipes have been drilled. The paste is granular, 
dirty-green or brown in colour, and seems generally to consist chiefly of comminuted 
basalt. 

b. Volcanic Conglomerates and Breccias in beds intercalated between the flows of 
Basalt. — These are of at least three kinds, (a) Basalt-conglomerates, composed mainly 
of rounded and subangular blocks of basalt (or allied basic lava), sometimes a yard or 
more in diameter, not unfrequently in the form of pieces of rough slag or even of true 
bombs, embedded in a granular matrix of comminuted basalt-debris. In some cases, the 
stones form by far the most abundant constituents of the rock, which then resembles 
some of the coarse agglomerates just described. On the east side of Mull, for example, 
the slaggy basalts of Beinn Chreagach Mhor are occasionally separated by materials of 
this character. But such intercalations are seldom more than a few feet or yards in 



82 DR GE1KIE ON THE HISTORY OF VOLCANIC ACTION 

thickness. Their coarseness and repetition on successive horizons show that they 
accumulated in the near neighbourhood of one or more small vents, from which discharges 
of fragmentary materials took place at the beginning or at the close of an outflow of 
lava. More commonly, however, the dirty-green or dark-brown granular matrix exceeds 
in bulk the stones embedded in it. It has obviously been derived mainly from the 
trituration of already cooled basalt-masses, and probably also from explosions of the still 
molten rock in the vents. As in the case of the agglomerates of the vents, pieces of 
older acid lavas, and still more of the non- volcanic rocks that underlie the plateaux, are 
found in these bedded conglomerates and breccias. In Antrim and Mull, for instance, 
fragments of flint and chalk are of common occurrence. A characteristic example of this 
kind of rock is to be seen forming the platform of the remarkable columnar bed out of 
which Fingal's Cave, Staffa, has been excavated. 

(/3) Felsitic Breccia and Conglomerate. — This variety is of rare occurrence, but it is 
to be seen in a number of localities in the island of Mull. It is composed in great 
measure of angular fragments of a close-grained flinty felsitic rock, with pieces of quartzite 
and amygdaloidal basalt, the dull dirty-green matrix appearing to be made up chiefly of 
basalt-dust. 

(y) Breccias of Non- Volcanic Materials. — These, the most exceptional of all the 
fragmentary intercalations in the plateaux, consist almost wholly of angular blocks of 
rocks which are known to underlie the basalts, but with a variable admixture of basalt 
fragments. They are due to volcanic explosions which shattered the subjacent older crust 
of rocks, and discharged fragments of these from the vents or allowed them to be borne 
upwards on an ascending column of basic lava. Pieces of the non-volcanic platform are of 
common occurrence among the fragmentary accumulations, especially in the lower parts 
of the plateaux- basalts. But I have never seen so remarkable an example of a breccia of 
this kind as that which occurs near the summit of Sgurr Dearg, in the east of Mull. The 
bedded basalt encloses a lenticular band of exceedingly coarse breccia, consisting mainly 
of angular pieces of quartzite, with fragments of amygdaloidal basalt. In the midst of 
the breccia lies a huge mass or cake of erupted mica-schist, at least 100 yards long by 
30 yards wide, as measured across the strike up the slope of the hill. To the west, owing 
to the thinning out of the breccia, this piece of schist comes to lie between two beds of 
basalt. A little higher up, other smaller but still large blocks of similar schist are involved 
in the basalt, as shown in fig. 19. As the huge cake of mica-schist plunges into the hill, 
its whole dimensions cannot be seen; but there are visible, at least, 15,000 cubic yards, 
which must weigh more than 30,000 tons. Blocks of quartzite of less dimensions occur 
in the basalts on Loch Spelve. There can be no doubt, I think, that these enormous 
fragments were torn off from the underlying crystalline schists which form the framework 
of the western Highlands, and were floated upward in an ascending flow of molten basalt. 
Had the largest mass occurred at or near the base of the volcanic series, its size and 
position would have been less remarkable. But it lies more than 2000 feet up in the 
basalts, and hence must have been borne upward for more than that height. A similar 



DUEING THE TEETIAEY PEEIOD IN THE BEITISH ISLES. 



83 



but less striking breccia occurs on the south coast of the same island, near Carsaig, made 
up chiefly of pieces of quartzite and quartz.* 

c. Tuffs. — So far as I am aware, all the tuffs intercalated in the basalt-plateaux 
consist essentially of basic materials, derived from the destruction of different varieties of 
basalt-rocks, though also containing occasional fragments of older felsitic rocks, as well 
as pieces of chalk, flint, quartz, and other non-volcanic materials. They are generally 
dull, dirty-green in colour, but become red, lilac, brown, and yellow, according to the 
amount and state of combination and oxidation of their ferruginous constituents. They 
usually contain abundant fragments of amygdaloidal and other basalts. As a rule, they 
are distinctly stratified, and occur in bands from a few inches to 50 feet or more in thick- 
ness. The matrix being soft and much decomposed, these bands crumble- away under 
the action of the weather, and contribute to the abruptness of the basalt-escarpments 
that so often overlie them. 

Where the tuffs become fine-grained and free from embedded stones, they pass into 
variously-coloured clays. Among these are the " beauxite " and " lithomarge " of Antrim. 







b da 

Fig. 19. — Breccia and Blocks of mica-schist, quartzite, &c, lying between bedded Basalts, Isle of Mull. 
a,a, Bedded basalts ; b, Breccia ; d, Basic dyke. 



Associated with these deposits in the same district, is a pisolitic haematite, which has 
been proved to occur over a considerable area on the same horizon. Many of the clays 
are highly ferruginous. The red streaks that intervene between successive sheets of 
basalt are of this nature (bole, plinthite, &c). The source of the iron-oxide is doubtless 
to be traced to the decomposition of the basic lavas during the volcanic period. 

d. There occur also grey and black clays and shales, of ordinary sedimentary 
materials, not infrequently containing leaves of terrestrial plants and remains of insects 
(leaf-beds), sometimes associated with impure limestones, but more frequently with sand- 
stones and indurated gravels or conglomerates containing pieces of fossil wood. These 
intercalated bands undoubtedly indicate the action of running water and the accumulation 
of sediment in hollows of the exposed flows of basalt at intervals during the piling up of 
the successive lava-sheets that form the plateaux. 

The vegetable matter has in some places gathered into lenticular seams of lignite, and 
* This is noticed by Mr Starkie Gardner, Quart. Jour. Geol. Soc, xliii. (1887) p. 283, note. 



84 DR 'GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

even occasionally of black glossy coal. Amber also has been found in the lignite. Where 
the vegetation has been exposed to the action of intrusive dykes or sheets, it has some- 
times passed into the state of graphite. 

The remarkable terrestrial flora found in the leaf-beds, and in association with the 
lignites, was first made known by the descriptions of Edward Forbes already referred 
to, and has more recently been studied and described by Heer, Mr Baily, and Mr Starkie 
Gardner.* It was regarded by Forbes as of Miocene age, and this view has generally 
been adopted by geologists. Mr Starkie Gardner, however, contends that it indicates a 
much wider range of geological time. He believes that a succession of floras may be 
recognised, the oldest belonging to an early part of the Eocene period. Terrestrial plants, 
it must be admitted, are not always a reliable test of geological age, and I am not yet 
satisfied that in this instance they afford evidence of such a chronological sequence as Mr 
Gardner claims, though I am convinced that the Tertiary volcanic period was long enough 
to have allowed of the development of considerable changes in the character of the 
vegetation. 

For the purpose of the present paper, however, the precise stage in the geological 
record, which this flora indicates, is of less consequence than the broad fact that the 
plants prove beyond all question that the basalts among which they he were erupted on 
land during the older part of the long succession of Tertiary periods. Their value in 
this respect cannot be overestimated. Stratigraphical evidence shows that the eruptions 
must be later than the Upper Chalk ; but the embedded plants definitely limit them to 
the earlier half of Tertiary time. 

§ 2. Areas of the Plateaux and Succession of Eocks in them. 

There are four districts in which the original widespread lava-fields have been less 
extensively eroded than elsewhere, or at least where they have survived in larger and 
thicker masses. Whether or not each of them was an isolated area of volcanic activity 
cannot now be determined. Their several outflows of lava may have united into one 
continuous volcanic tract, and their present isolation may be due entirely to subterranean 
movements and denudation. There is a certain convenience, however, in treating 
them separately. They are — 1. Antrim; 2. Mull; 3. Small Isles ; 4. Skye. To these 
might be added the Shiant Isles and St Kilda. 

1. AntrimA — The largest of the basalt-plateaux of Britain is that which forms so 
prominent a feature in the scenery and geology of the north of Ireland, stretching from 
Lough Foyle to Belfast Lough, and from Bathlin Island to beyond the southern margin 
of Lough Neagh. Its area may be roughly computed at about 2000 square miles. But, 

* Mr Gardner is now describing and illustrating the flora fully for the Palasontographical Society; see vols, 
xxxviii., xxxix. et seq. 

t The basalts of Antrim are the subject of an abundant literature. I may refer particularly to the papers of 
Berger and Conybeare (Trans. Geol. Soc, iii.), the Geological Report of Portlock, and the Explanations of the Sheets 
of the Geological Survey of Ireland. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 85 

as it's truncated strata rise high along its border, and look far over the low grounds on 
every side, it must be regarded as a mere fragment of the original volcanic plain. It 
may be described as an undulating tableland, which almost everywhere terminates in a 
range of bold cliffs, but which, towards the centre and south, sinks gently into the basin 
of Lough Neagh. The marginal line of escarpment, however, presents considerable 
irregularity both in height and form, besides being liable to frequent local interruptions. 
It is highest on the west side, one of its crests reaching at Mullaghmore, in county 
Londonderry, a height of 1825 feet. On the north, it sinks down into the valley of the 
Bann, east of which it gradually ascends, forming the well-known range of cliffs from the 
Giant's Causeway and Bengore Head to Ballycastle. It then strikes inland, and making 
a wide curve in which it reaches a height of more than 1300 feet, comes to the sea again 
at Garron Point. From that headland the cliffs of basalt form a belt of picturesque 
ground southwards beyond Belfast, interrupted only by valleys that convey the drainage 
of the interior of the plateau to the North Channel. Above the valley of the Lagan the 
crest of the plateau rises to a height of more than 1500 feet. 

Throughout most of its extent the basalt-escarpment rests on the white limestone or 
Chalk of Antrim, beneath which lie soft Lias shales and Triassic marls. Here and there, 
where the substratum of Chalk is thin, the action of underground water in the crumbling 
shales and marls below it has given rise to landslips. The slopes beneath the base of the 
basalt are strewn with slipped masses of that rock, almost all the way from Cushendall to 
Larne, some of the detached portions being so large as to be readily taken for parts of 
the unmoved rock. On the west side also, a group of huge landslips cumbers the 
declivities beneath the mural front of Benevenagh. 

I have found some difficulty in the attempt to ascertain what ; was the probable form 
of surface over which the volcanic rocks of this plateau began to be poured out. The 
Chalk sinks below the sea-level on the north coast, but, in the outlier of Slieve Gallion, 
three miles beyond the western base of the escarpment, it rises to a height of 1500 feet 
above the sea. On the east side also, it shows remarkable differences of level. Thus, 
below the White Head at the mouth of Belfast Lough, it passes under the sea-level, but 
only 16 miles to the south, where it crops out from under the basalt, its surface is about 
1000 feet above that level. If these variations in height existed at the time of the out- 
pouring of the basalt, the surface of the ground over which the eruptions took place was 
so irregular that some hundreds of feet of lava must have accumulated before the higher 
chalk hills were buried under the volcanic discharges. But it seems to me that much of 
this inequality in the height of the upper surface of the Chalk is to be attributed to 
unequal movements since the volcanic period, which involved the basalt in their effects, 
as well as the platform of Chalk below it. Had the present undulations of that platform 
been older than the volcanic discharges, it is obvious that upper portions of the basalt- 
series would have overlapped lower, and would have come to rest directly on the Chalk. 
But this arrangement, so far as I am aware, never occurs, except on a trifling scale. 
Wherever the Chalk appears, it is covered by sheets of the lower and not of the upper of 

VOL. XXXV. PART 2. M 



86 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

the two groups into which the Antrim basalts are divisible. We have actual proof of 
considerable terrestrial disturbance, subsequent to the date of the formation of the 
volcanic plateau. Thus, near Ballycastle, a fault lets down the basalt and its Chalk 
platform against the crystalline schists of that district. On the east side of the fault, the 
Chalk is found far up the slope, and circling round the base of the beautiful cone of 
Knocklayd — an outlier of the basalt which reaches a height of 1695 feet. The amount 
of vertical displacement of the volcanic sheets is here 700 feet.* Many other displace- 
ments, as shown by the mapping of my colleagues in the Geological Survey, have shifted 
the base of the escarpment from a few inches up to several hundred feet. 

It is evident, therefore, that the present position of the Chalk platform is far from 
agreeing with that which it presented to the outflow of the sheets of basalt. But, on the 
other hand, there can be no doubt that its surface at the beginning of th evolcanic out- 
bursts was not a level plain. It was probably a rolling country of low bare chalk-downs, 
like parts of the south-east of England. The Chalk attains its maximum thickness of 
perhaps 250 feet at Ballintoy. But it is liable to rapid diminution. On the shore at 
Ballycastle, about 150 feet of it can be seen, its base being concealed ; but only 2\ miles 
to the south, on the outlier of Knocklayd, the thickness is not quite half so much. On 
the west side of the plateau also, there are rapid changes in the thickness of Chalk. Such 
variations appear to be mainly attributable to unequal erosion before the outflow of the 
basalts. So great indeed had been the denudation of the Cretaceous and underlying 
Secondary formations previous to the beginning of the volcanic outbursts, that in some 
places the whole of these strata had been stripped off the country, so that the older 
platform of Palaeozoic or still more ancient masses was laid bare. Thus, on the west side 
of the escarpment, the basalt steals across the Chalk and comes to rest directly upon 
Lower Carboniferous rocks. 

The authors who have described the junction of the Chalk and basalt in Antrim have 
generally referred to the uneven surface of the former rock as exposed in any given section. 
The floor on which the basalt lies is remarkably irregular, rising into ridges and sinking 
into hollows or trenches, but almost everywhere presenting a layer of earthy rubbish made 
of brown ferruginous clays, mixed with pieces of flint, chalk, and even basalt.t The 
flints are generally reddened and shattery. The chalk itself has been described as 
indurated, and its flints as partially burnt by the influence of the overlying basalt. But 
I have not noticed, at any locality, evidence of alteration of the solid chalk, except where 
dykes or intrusive sheets have penetrated it.| There can be no doubt that the hardness 
of the rock is an original peculiarity, due to the circumstances of its formation. The 
irregular earthy rubble, that almost always intervenes between the chalk and the base of 
the basalt, like the " clay with flints " so general over the Chalk of southern England, no 

* Explanatory Memoir of Sheets 7 and 8, Geological Survey, Ireland, by Messrs Symes, Egan, and M'Henby 
(1888), p. 37. 

+ Portlock, Report on Geology of Londonderry, &c. (Geological Survey), p. 117. 
X See Portlock, op. cit., p. 116. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 87 

doubt represents long-continued subserial weathering previous to the outflow of the 
basalt. Even, therefore, if there were no other evidence, we might infer with some con- 
fidence from this layer of rubble, that the surface over which the lavas were poured was a 
terrestrial one. 

The Antrim plateau is not only the largest in the British Islands, it is also the most 
continuous and regular. It may be regarded, indeed, as one unbroken sheet of volcanic 
material, with no such mountainous masses of eruptive rock as in the other plateaux 
disturb the continuity of the horizontal or gently inclined sheets of basalt. Around its 
margin, indeed, a few outliers tower above the plains, and serve as impressive memorials 
of its losses by denudation. Of these, by much the most picturesque and imposing, 
though not the loftiest, is Knocklayd already referred to, which forms so striking a feature 
in the north-east of Antrim. 

The total thickness of volcanic rocks in the Antrim plateau exceeds 1000 feet; but r 
as the upper part of the series has been removed by denudation, the whole depth of lava 
originally poured out cannot now be told. A well-marked group of tuffs and clays, 
traceable throughout a large part of Antrim, forms a good horizon in the midst of the 
basalts, which are thus divisible into a lower and upper group. 

The Lower Basalts have a thickness of from 400 to 500 feet. But, as already 
mentioned (p. 80), they rapidly die out in about six miles to no more than 40 feet at 
Ballintoy. They are distinguished by their general cellular and amygdaloidal character, 
and less frequently columnar structure. The successive flows, each averaging perhaps 
about 15 feet in thickness, are often separated by thin red ferruginous clayey partings, 
sometimes by bands of green or brown fine gravelly tuff. The most extensive sheet of 
tuff is one which occurs in the lower part of the group at Ballintoy, and can be traced 
along the coast for about five miles. In the middle of its course, near the picturesque 
Carrick-a-raide, it reaches a maximum thickness of about 100 feet, and gradually dies out 
to east and west. The neck of coarse agglomerate at Carrick-a-raide, already referred 
to, is doubtless the vent from which this mass of tuff was discharged (see fig. 29). 
Owing to the thinning out of the sheets of basalt, as they approach the vent, the tuff 
comes to rest directly on the Chalk, and for some distance westwards forms the actual 
base of the volcanic series. * Occasional seams of carbonaceous clays, or even of lignite, 
appear on different horizons. Beneath the whole mass of basalt, indeed, remains of 
terrestrial vegetation here and there occur. Thus, near Banbridge, county Down, a 
patch of lignite, 4 feet 1 inches thick, underlies the basalt, and rests directly on Silurian 
rocks. Such fragmentary records are an interesting memorial of the wooded land-surface 
over which the earliest outflows of basalt spread. 

The central zone of tuffs, clays, and iron-ore is generally from 30 to 40 and sometimes 
as much as 70 feet thick. From the occurrence of the ore in it, this zone has been 
explored more diligently in recent years than any other group of rocks in Antrim, and 
its outcrop is now known over most of the district in which it occurs. The iron-ore bed 

* See Explanation of Sheets 7 and 8 of the Geological Survey of Ireland (1888), p. 23. 



88 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

varies from less than an inch up to 18 inches in thickness, and consists of pisolitic 
concretions of hrematite, from the size of a pea to that of a hazel nut, wrapped up in a 
soft ochreous clayey matrix. Where it is absent, its place is sometimes taken by an 
aluminous clay, worked as "beauxite," which has yielded stumps of trees and numerous 
leaves and cones. Beneath the iron-ore, or its representative, lies what is called the 
" pavement," — a ferruginous tuff, 8 to 10 feet thick, resting on " lithomarge," — a lilac or 
violet mottled aluminous earth sometimes full of rounded blocks or bombs of basalt. 
The well-known horizon for fossil plants at Ballypallidy is a red tuff in this zone. 

This intercalated band of ferruginous deposits forms one of the most persistent and 
interesting features in the Antrim plateau. The actual area now occupied by it has 
been so reduced by denudation into mere scattered patches that it probably does not 
exceed 170 square miles. But the zone can be traced from Divis Hill, near Belfast, to 
Rathlin Island, a distance of 50 miles, and from the valley of the Bann to the coast above 
Glen arm, more than 20 miles. There can be little doubt that it was once continuous over 
all that area, and that it probably extended some way further on all sides. Hence, the 
original area over which the iron-ore and its accompanying tuffs and clays were laid 
down can hardly have been less than 1000 square miles. This extensive tract was 
evidently the site of a lake during the volcanic period, formed by a subsidence of the 
floor of lower basalts. The salts of iron contained in solution in the water, whether 
derived from the decay of the surrounding lavas or from the discharges of chalybeate 
springs, were precipitated as peroxide in pisolitic form, as similar ores are now being 
formed on lake-bottoms in Sweden. For a long interval, quiet sedimentation went on 
in this lake, the only sign of volcanic energy during that time being the dust and stones 
that were thrown out and fell over the water-basin, or were washed into it by rains from 
the slopes around. 

Immediately above the iron-ore, or separated from it in places by only a few inches 
of tuff, comes the group of Upper Basalts, which varies up to 600 feet in thickness, 
though, as the upper portion has been everywhere removed by denudation, no measure 
remains of what may have been the original depth of the group. The general character 
of these basalts is more frequently columnar, black and compact, and with fewer examples 
of the strongly amygdaloidal structure so conspicuous in the lower group. But this 
distinction is less marked in the south than in the north of Antrim, so that where the 
intervening zone of tuffs and iron-ore disappears, no satisfactory line of division can be 
traced between the two groups of basalt. The occurrence of that zone, however, by 
giving rise to a hollow or slope, from which the upper basalts rise as a steep bank or 
cliff, furnishes a convenient topographical feature for mapping the boundary of these 
rocks. Among the upper basalts, also, there is perhaps a less frequent occurrence of 
those thin red partings of bole between the successive flows, so conspicuous in the lower 
group. But the flows are not less distinctly marked off from each other. Nowhere can 
their characteristic features be better seen than along the magnificent range of cliffs from 
the Giant's Causeway eastwards. The columnar bed that forms the Causeway is the 



DURING THE TERTIARY PERIOD IN" THE BRITISH ISLES. 89 

lowest sheet of the upper group, and may be seen resting directly on the zone of grey and 
red tuffs. It is about 60 or 70 feet thick ; and, while perfectly regular in its columnar 
structure at the Causeway and the " Organ," assumes further eastward the confusedly 
starch-like arrangement of prisms already referred to. But, in the great cliff section of 
the " Amphitheatre," the more regular structure is resumed, the bed swells out to about 80 
feet in thickness, and columns of that length run up the face of the precipice, weathering 
out at the top into separate pillars, which, perched on the crest of an outstanding ridge, 
are known as the " Chimneys." The basalt-beds that succeed the lowest one are each 
only about 15 to 20 feet thick. 

Between the successive sheets of the upper basalts thin seams of red ferruginous clay, 
though, as I have said, less frequent perhaps than in the lower group, continue to show 
that the intervals between successive eruptions were of sufficient duration to admit of 
considerable subserial decay of the surface of a lava before the outflow of the next bed. 
Occasional thin layers of tuff also, and even of pisolitic iron-ore, have been observed 
among these higher basalts. But the most interesting and important intercalations are 
inconstant seams of lignite. One of the most conspicuous of these lies immediately 
above the basalt of the " Causeway," where it was long worked for fuel, and was found 
to be more than 6 feet thick. But it is quite local, as may be seen at the " Organ " over 
which it lies, with a thickness of only 12 inches, rapidly dying out so as to allow 
the basalts above and below it to come together. The removal of the upper portion 
of the basalts prevents us from carrying the volcanic history of the Irish plateau 
further. 

It is obvious that nowhere in Antrim does any trace exist of a central vent or cone 
from which the volcanic materials were discharged. There is no perceptible thickening 
of the individual basalt sheets, nor of the whole series in one general direction, in such a 
manner as to point to the site of some chief focus of eruption. Nor can we place reliance 
on the inclination of the several parts of the plateau. I have pointed out that the varying 
dip of the beds must be attributed mainly to post-volcanic movements, or at least to 
movements which, if not later than all the phases of volcanic action, must have succeeded 
the outpouring of the plateau-basalts. There has been a general subsidence towards the 
central and southern portions of the plateau, and this movement has no doubt given rise 
to the hollow that is now occupied by Lough Neagh. But nowhere in the depression is 
there any trace of the ruins of a central cone or focus of discharge. 

The Antrim plateau, in these respects, resembles the others. But it differs from them 
in one important particular. It has nowhere been disrupted by huge eruptive bosses of 
younger rocks, such as have broken up the continuity of the old lava-fields further north. 
Yet it is not without its memorials also of these younger protrusions. It has some feeble 
representatives of the great acid bosses of the Inner Hebrides, and it contains not a few 
excellent examples of true volcanic vents. To these fuller reference will be made in later 
pages. 

2. Mull. — This plateau, besides the island of Mull, embraces a portion of Morven, 



90 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

and, stretching across Loch Sunart, includes the western part of the peninsula of Ardna- 
murchan. That it formerly extended far beyond its present limits is impressively 
indicated by its margin of cliff's and fringe of scattered islands and outliers. It went 
west, at least, as far as the Treshnish Isles, which are composed of basalt. On its eastern 
border, a capping of basalt on the top of Ben Iadain (1873 feet) in Morven, and others 
further north, prove that its volcanic sheets once spread far into the interior of Argyle- 
shire (fig. 20). On the south, its fine range of lofty cliffs, with their horizontal bars of 
basalt, bear witness to the diminution which it has undergone on that side ; while, on 
the north, similar sea-walls tell the same tale. Not only has it suffered by waste along its 
margin, it has also been deeply trenched by the excavation of glens and arms of the sea. 
The Sound of Mull cuts it in two, and the mainland portion is further bisected by Loch 
Sunart, and again by Loch Aline. The island of Mull is so penetrated by sea-lochs that 
a comparatively slight depression would turn it into a group of islands. But, besides 
its enormous denudation, the Mull plateau has been subjected to great disruption from 




Fig. 20. — Basalt-Capping on top of Ben Iadain, Morven. 

subterranean movements. In the southern portion of the island, it has been broken up 
by the intrusion of large bosses and sheets of gabbro, and by masses as well as innumer- 
able veins of various granitoid and felsitic rocks. In Ardnamurchan, it has suffered so 
much disturbance from the sama cause that its original structure has been almost 
obliterated over a considerable area. Moreover, it has been dislocated by many faults, 
by which different portions have been greatly shifted in level. The most important of 
these breaks is one noticed by Professor Judd, and visible to every tourist who sails up 
the Sound of Mull. It traverses the cliffs on the Morven side, opposite Craignure, 
bringing the basalts against the crystalline schists, and strikes thence inland, wheeling 
round into the long valley in which Lochs Arienas and Teacus lie. On its western side, 
the base of the basalt-series is almost at the sea-level ; on its eastern side, that platform 
rises high into the outliers of Beinn na h-Uamha (1521 feet) and Beinn Iadain. The 
amount of displacement here is probably not much less than 1500 feet. Many other 



DURING THE TERTIARY PERIOD IN" THE BRITISH ISLES. 91 

minor faults in the same district show how much the crust of the earth has been fractured 
here since older Tertiary time.* 

Nevertheless, in spite of the extent to which the Mull plateau has suffered from 
denudation and subterranean disturbance, and indeed in consequence thereof, this 
plateau presents clear sections of many features in the history of the basalt-outflows and 
of the subsequent phases of Tertiary volcanic action which cannot be seen in the more 
regular and continuous tableland of Antrim. Moreover, it still possesses in its highest 
mountain, Ben More (3169 feet), a greater thickness and a higher series of lavas than 
can now be seen in any other of the plateaux. 

It will be readily understood that, in the case of this plateau, the difficulties already 
referred to in regard to that of Antrim, of tracing the probable form of ground on which 
the volcanic eruptions began, are considerably increased. We can dimly perceive that 
the depression in the crystalline rocks of the Highlands which had, from at least the older 
part of the Jurassic period, stretched in a N.N. W. direction along what is now the western 
margin of Argyleshire, lay beneath the sea in Jurassic time, and was then more or less 
filled up with sedimentary deposits. The hollow appears thereafter to have become 
a land-valley, whence much of the Jurassic strata was cleared out by denudation before 
its subsequent submergence under the sea in which the upper Cretaceous deposits 
accumulated. Professor Judd has shown how relics of these Cretaceous strata appear on 
both sides of the plateau from under the protecting cover of basalt-sheets. But, before 
the volcanic eruptions began, the area had once again been raised into land, and the 
youngest Secondary formations had been extensively eroded. 

In their general aspect the basalts of Mull agree with those of Antrim, and the 
circumstances under which they were erupted were no doubt essentially the same. But 
considerable differences in detail are observable between the succession of rocks in the 
two areas. The total depth of basalt-sheets in Mull is greater than in any other of the 
plateaux. When I first visited the island in 1866, the only available maps, with any 
pretensions to accuracy, were the Admiralty charts ; but, as these do not give the interior 
except in a generalised way, it was difficult to plot sections from them, and to arrive at 
satisfactory conclusions as to the thickness of different groups of rock. Accordingly, as 
the successive nearly flat flows of basalt can be traced from the sea-level up to the top of 
Ben More, I contented nryself with the fact that the total depth of lava-beds in Mull was 
at least equal to the height of that mountain, or 3169 feet. The publication of the 
Ordnance Survey Maps now enables us to make a nearer approximation to the truth. 
From the western base of the magnificent headland of Gribon, the basalts in almost 
horizontal beds rise in one vast sweep of precipice and terraced slope to a height of over 
1600 feet, and then stretch eastwards to pass under the higher part of Ben More, at 
a distance of some 8 miles. They have a slight easterly inclination, so that the basement 

* There are no fewer than three faults in the basalt-capping on the summit of Ben Iadain. By bringing the 
basalts and schists into juxtaposition, they have given rise to topographical features that can be seen even from a 
distance. See fig. 20. 



92 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

beds seen at the sea-level, at the mouth of Loch Scridain, gradually sink below that level 
as they go eastward. It is not easy to get a measurement of dip among these basalts, 
except from a distance. If we take the inclination at only 1°, the beds which are at the 
base of the cliff on the west, must be about 700 feet below the sea on the line of Ben 
More, which would give a total thickness of nearly 3900 feet of bedded lava below the 
top of that mountain. We shall not probably overestimate the thickness of the Mull 
plateau if we put it at 3500 feet. 

The base of the volcanic series of Mull can best be seen on the south coast at Carsaig, 
and at the foot of the precipices of Gribon. As already stated, it is there found resting 
above Cretaceous and Jurassic rocks. The lowest beds are basalt-tuffs, of the usual dull- 
green colour. They are in places much intermingled with sandy and gravelly sediment, 
as if the volcanic debris had fallen into water where such sediment was in course of 
deposition. One of the most interesting features, indeed, in this basement part of the 
series, is the occurrence of bands of non- volcanic material which accumulated after the 
tuffs and some of the lavas had been erupted, but before the main mass of basalts. 
Those at Carsaig include a lenticular bed, 25 feet thick, of rolled flints, which, with 
some associated sandy bands, lies between sheets of basalt. On the opposite side of the 
promontory is the well-known locality of Ardtun, from which the first land-plants in the 
volcanic series were determined. The actual base of the basalts is not there seen, being 
covered by the sea. The " leaf-beds," with their accompanying sandstones, gravels, and 
limestone, lie upon a sheet of basalt, which in some parts is exceedingly slaggy on the 
top, passing down into a black compact basalt, and assuming at the base of the cliff a 
columnar arrangement, with the prisms curved and built up endways towards each other. 
Some of the gravels exceed 30 feet in thickness, and consist of rolled flints, bits of chalk, 
and pieces of basalt, and of other basic igneous rocks. But some of their most interest- 
ing ingredients are pebbles of sanidine lavas, which have been recognised in them by Mr 
G. Cole.* No known protrusions of such lavas occur anywhere beneath or interstratified 
with the plateau-basalts. As will be afterwards shown, all the visible acid rocks, the 
geological relations of which can be ascertained, are of younger date than these basalts. 
I am disposed to regard the fragments found in the Ardtun conglomerates as probably 
derived from some of the basalt-conglomerates of the plateau, in which fragments of 
siliceous igneous rocks do occur. Though there is no evidence that any lavas of that 
nature were poured out at the surface before or during the emission of the basalts, the 
contents of these fragmental volcanic accumulations prove that such lavas, already 
consolidated, lay at some depth beneath the surface, and that fragments were torn off 
from them during the explosions that threw out the materials of the basalt-conglomerates 
to the surface. 

Mr Stark ie Gardner has called attention to the extraordinarily fresh condition of 
the vegetation in some of the layers of the Ardtun section. One of the leaf-beds he has 
found to be made up for an inch or two of a pressed mass of leaves, lying layer upon 

* Quart. Jour. Geol. Soc, xliii. (1887) p. 277. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 93 

layer, and retaining almost the colours of dead vegetation. Among the plants represented 
is a large purple Ginkgo and a fine Platanites, one leaf measuring 15^ inches long by 
10^ broad. The characteristic dicotyledonous leaves at this locality possessed relatively 
large foliage.* 

To the early observations of Macculloch we are indebted for the record of an 
interesting fact in connection with the vegetation of the land-surface over which the first 
lava-flows spread. He figured a vertical tree trunk, imbedded in prismatic basalt, and 
rightly referred it to some species of fir.t This relic may still be seen under the basalt- 
precipices of Gribon. Mr Gardner found it to be "a large trunk of a coniferous tree, 
five feet in diameter, perhaps Podocarpus, which has been enveloped, as it stood, in one 
of the flows of trap to the height of 40 feet. Its solidity and girth evidently enabled it 
to resist the fire, but it had decayed before the next flow passed over it, for its trunk is 
a hollow cylinder filled with debris, and lined with the charred wood. A limb of another, 
or perhaps the same tree, is in a fissure not far off." \ 

At different levels in the volcanic series of Mull, beds of lignite and even true coal 
are observable. These seem to be always mere lenticular patches, only a few square yards 
in extent. The best example I have met with is among the basalts near Carsaig. It is 
in part a black glossy coal, and partly dull and shaly. Some years ago it was between 
two and three feet thick, but now, owing to its having been dug away by the shepherds, 
only some six or eight inches are to be seen. It lies between two basalt-flows, and 
rapidly disappears on either side. 

More frequent than these inconstant layers of fossil vegetation are the thin partings 
of tuff and layers of red clay, sometimes containing iron-ore, which occur at intervals 
throughout the series between different flows of basalt. But even such intercalations are 
of trifling thickness, and only of limited extent. The magnificent precipices of M'Gorry's 
Head and Gribon expose a succession of beds of columnar amorphous and amygdaloidal 
basalt, which must attain a thickness of at least 2500 feet, before they are overlain by the 
higher group of lavas in Ben More. On the east side of the island, thin tuffs and bands 
of basalt-conglomerate occur on different horizons among the bedded basalts, from near 
the sea-level up to the summit of the ridge which culminates in Beinn Meadhon (2087 
feet), Dun-da-Ghaoithe (2512 feet), and Mainnir-nam-Fiadh (2483 feet). 

Above the ordinary compact and amygdaloidal basalt comes the higher pale group 
already referred to as forming the uppermost part of Ben More, whence it stretches 
continuously along the pointed ridge of A'Chioch, and thence northwards into Beinn 
Fhada. The same felspathic lavas are likewise found in two outliers, capping Beinn a' 
Chraig, a mile further north, and I have found fragments of them on some of the loftier 
ridges to the south-east. This highest and youngest group of lavas in the plateaux has 
been reduced to mere isolated patches, and a little further denudation will remove it 

* For fuller local details regarding the Ardtun leaf-beds, I may refer to the original paper by the Duke of Argyll 
{Quart. Jour. Geol. Soc., vii. p. 89), and to the recent memoir by Mr Starkie-Gardner (op. cit., xliii., 1887, p. 270). 
t Western Islands, vol. i. p. 568, and plate xxi. fig. 1. % Quart. Jour. Geol. Soc, xliii. p. 283. 

VOL. XXXV. PART 2. N 



94 DR G'EIKIE ON THE HISTORY OF VOLCANIC ACTION 

altogether. Yet it is not less than about 800 feet thick, and consists of bedded lavas, 
which alternate with and follow continuously and conformably upon the top of the 
ordinary plateau-basalts. I have described these rocks as dull, finely crystalline or compact, 
light-grey in colour, and weathering with a characteristic platy form, which has been 
mistaken for the bedding of tuffs. The fissility, however, has none of the regularity or 
parallelism of true bedding, and may be observed to run sometimes parallel with the bed- 
ding of the sheets, sometimes obliquely or even at right angles to it. Even where this 
structure is best developed, the truly crystalline nature of the rocks can readily be 
detected. Some of them are porphyritic and amygdaloidal, the very topmost bed of the 
mountain being a coarse amygdaloid. Intercalated with these curious rocks there are others 
in which the ordinary characters of the dolerites and basalts of the plateaux can be 
recognised. The amygdaloids are often full of delicate prisms of epidote. 

In Mull, as in the other areas of terraced basalts, we everywhere meet with gently 
inclined sheets, which do not thicken out individually or collectively in any given direction, 
except as the result of unequal denudation. So far as I have been able to discover, they 
afford no evidence of any great volcanic cone from which they proceeded. Their present 
inclinations are unquestionably due, as in Ireland, to movements subsequent to the 
formation of the plateau. In Loch-na-keal they dip gently to the E.N.E. ; in Ulva and 
the north-west coast to N.N.E. ; near Salen to W.S.W. on the one side, and N.W. on the 
other. Round the southern and eastern margins of the mountainous tract of the island, 
they dip generally inwards to the high grounds. 

The Mull plateau presents a striking contrast to that of Antrim, in the extraordinary 
extent to which it has been disrupted by later protrusions of massive basic and acid 
rocks over a rudely circular area, extending from the head of Loch Scridain to the Sound 
of Mull, and from Loch-na-keal to Loch Buy. The bedded basalts have been invaded 
by masses of dolerite, gabbro, and granophyre, with various allied kinds of rock. They 
have not only been disturbed in their continuity, but have undergone considerable 
metamorphism. 

Again, further to the north, in the promontory of Ardnamurchan, the plateau has 
been disrupted in a similar way, and only a few recognisable fragments of it have been 
left. These changes will be more appropriately discussed in connection with similar 
phenomena in the other plateaux further north. 

3. Small Isles. — This plateau, the smallest and most discontinuous of the four, 
includes the islands of Eigg, Rum, Canna, and Muck, which form the parish of Small 
Isles. That the fragments of the bedded volcanic masses, preserved on each of these 
islands, were once connected can hardly be doubted. Indeed, as already stated, they 
were not improbably united with the plateau of Skye on the north, and with that of 
Ardnamurchan and Mull on the south. Taking the whole space of land and sea within 
which the basalt of Small Isles is now confined, we may compute it at not much less than 
200 square miles. In Eigg, Muck, and Canna, the basalts retain their almost horizontal 
position, and from underneath them emerge the Jurassic strata on which they lie. The 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 95 

central part of the plateau, forming the island of Rum, is, however, much less regular. 
Four small outliers of the basalts lie at levels of 1200 feet and upwards, on the western 
slope of that island. They are underlain by a thick mass of red (Cambrian or Torridon) 
sandstones, which form the northern half of the island, and which southwards are 
connected with a confused series of gneisses and schists. These rocks are doubtless a 
continuation of the red sandstones and schists of Sleat, in Skye, and like them have been 
subjected to those post-Silurian convolutions and metamorphism whereby Archaean 
gneisses have been brought above younger rocks, and the whole have been crushed and 
rolled out so as to assume a new schistose arrangement. Before the time when volcanic 
action began, a mass of high ground, consisting of these ancient rocks, stood where the 
island of Rum is now situated. The streams of basalt spread around it, not only covering 
the surrounding low tracts of Jurassic rocks, but gradually accumulating against the hills, 
and thus reducing them both in area and in height above the plain.* 

The plateau has been obliterated over the centre and south of Eum by the extrusion 
of enormous masses of gabbro, and some later granitoid rocks. The most extensive of 
its fragmentary portions is that of Eigg, where the sheets of basalt, resting on Jurassic 
beds and dipping gently southwards, can be studied all round the island in a continuous 
range of precipices (see fig. 62). 

The general aspect and succession of volcanic sheets in the area of Small Isles agree 
with those of Antrim and of the older part of the plateau of Mull. The basalts in Eigg, 
Canna, and Muck rise into ranges of fine sea-walls, sometimes five or six hundred feet 
high. The thickest mass of them occurs in Eigg, where, lying unconformably upon 
different platforms of the Jurassic rocks, they attain a thickness of about 1100 feet. 
They consist of the usual types — black, fine-grained, columnar and amorphous basalts, 
more coarsely crystalline dolerites, and dull earthy amygdaloids with red partings, and 
occasional thin bands of basalt-conglomerate or tuff. The individual beds range in 
thickness from 20 to 50 or 60 feet. Though they seem quite continuous when looked at 
from the sea, yet, on closer examination, they are found not unfrequently to die out, 
the place of one bed being taken by another, or even by more than one, in continuation of 
the same horizon. The only marked petrographical variety which occurs among them is a 
light-coloured band which stands out conspicuously among the darker ordinary sheets of 
the escarpment on the east side of the island. The microscopic characters of this rock show 
it to belong to the same series of highly felspathic lavas as the " pale group " of Ben 
More, in Mull. It is strongly vesicular, and the cells are in some parts so flattened and 
elongated as to impart a kind of fissile texture to the bed.t 

This plateau has suffered even more than that of Mull from the combined influence 

* That the lava-fields did not completely bury this nucleus of older rock has been supposed to be shown by the 
fragments of red sandstone found in the ancient river-bed of Eigg, which, was scooped out of the basalt-plateau and 
sealed up under pitchstone. But I am disposed to think that these fragments, together with those of Jurassic sandstone, 
came, not from Rum, but from some district more to the north and east, as will be adverted to in a later part of this 
paper. 

+ For further details regarding this plateau in Eigg, see my paper, Quart. Jour. Geol. Soc. xxvii. (1871) p. 290. 



96 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

of later intrusive bosses and of prolonged denudation. That it once extended over the 
site of the whole of Rum can hardly be doubted. The edges of the beds that form the 
outliers would, if prolonged, cover the northern or lower half of the island, where the 
ancient Palaeozoic and Archaean rocks form the surface. In the southern half, the 
continuity of the basalts has been partly obscured and partly destroyed by the protrusion 
of the great masses of gabbro that form the singularly picturesque mountain group to 
which this island owes its prominence as a land-mark far and wide along the west coast 
of Scotland. 

4. Skye. — This is the largest and geologically most important of all the Scottish 
plateaux. Comprising the island of Skye, at least as far south as Loch Eishort, the west 
side of Scalpa and the southern half of Raasay, and probably extending to the Shiant 
Isles, it may be reckoned to embrace an area of not less than 800 square miles. The 
evidence that its limits are now greatly less than they originally were is, like that of 
Mull, abundant and impressive. Its truncated edges, rising here and there for a thousand 
feet as a great sea-wall above the breakers at their base, and presenting everywhere their 
succession of level or gently inclined bars of basalt-beds, are among the most stupendous 




Fig. 21.— Terraced Hills of Basalt Plateau (Macleod's Tables), Skye. 

monuments of denudation in this country. But still more striking to the geologist is the 
proof, furnished along the eastern margin of the plateau, that the Jurassic and other 
older rocks there visible were originally buried deep under the basalt-sheets, which have 
thus been entirely stripped off that part of the country. 

Throughout most of the district, wherever the base of the basalts can be seen, it is 
found to rest upon some member of the Jurassic series, but with a complete unconforma- 
bility. The underlying sedimentary strata had been dislocated and extensively denuded 
before the volcanic period began. On the southern margin, however, the red (Cambrian 
or Torridon) sandstones emerge from under the basalts of Loch Scavaig, and extending 
into the island of Soay are no doubt prolonged under the sea into Rum. This ridge 
probably represents the range of the ancient high ground of the latter island already 
referred to. 

Nowhere are the distinctive topographical features and geological structure of the 
1>; ^alt-plateaux more impressively displayed than in the northern half of the island of 
Skye. The green terraced slopes, with their parallel bands of brown rock formed by the 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



97 



outcrop of the nearly flat basalt-beds, rise from the bottoms of the valleys into flat-topped 
ridges and truncated cones (fig. 21). The hills everywhere present a curiously tabular 
form that bears witness to the horizontal sheets of rock of which they are composed* 
And along the stupendous sea-precipices, each successive sheet of basalt can be counted 
from base to summit, and followed from promontory to promontory (fig. 22). In the 
district of Trotternish, the basalt hills reach a height of 2360 feet. Further west, the 
singular flat-topped eminences, called "Macleod's Tables" (fig. 21), ascend to 1600 
feet. 

Along the western side of Skye, the basalts descend beneath the level of the Atlantic. 
Along the eastern side their base runs on the top of the great Jurassic escarpment, whose 
white and yellow sandstones form there, and on the east side of Eaasay, so prominent a 
feature in the landscape. To the south-east, the regularity of the volcanic plateau is 
effaced, as in Mull and Ardnamurchan, by the protrusion of the extensive mass of eruptive 
rocks constituting the Cuillin and Red Hills, east of which the basalts have been almost 








Fig. 22.— "Macleod's Maidens " and part of Basalt Cliffs of Skye. 

entirely removed by denudation, so as to expose the older rocks which they once covered, 
and through which the later eruptive bosses made their way. This is undoubtedly the 
most instructive district for the study of that later phase in the volcanic history of 
Britain comprised in the eruptive bosses of basic and acid rocks. 

The magnificent plateau of this island has been so profoundly cut down into glens 
and arms of the sea, and its component layers are exposed along so many leagues of 
noble precipice, that its structure is perhaps more completely laid open than that of any 
of the other areas. It is built up of a succession of basalts and dolerites of the usual 
types, which probably reach a thickness of more than 2000 feet, though in their instance, 
also, denudation has left only a portion of them, without any evidence by which to reckon 
what their total original depth may have been. In rambling over Skye, the geologist is 
more than ever struck with the remarkable scarcity and insignificance of the interstrati- 
fications of tuff or of any other kind of sedimentary deposit between the successive lava- 

* These features are more fully described in my Scenery of Scotland, 2d edit. (1887), pp. 74, 145, 216. 



98 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



sheets. In many places, indeed, bands of dirty-green tuff or basalt-conglomerate may 
be observed, sometimes, as at Portree harbour, associated with lenticular seams of coal, 
from a few inches to three feet in thickness. Sheets of finer tuff of brighter colours, 
violet, bluish, and red, like those of Antrim, form conspicuous features in some of the 
western sea-cliffs, as at Talisker. But compared with the enormous area and thickness 
of the basalts, these fragmentary ejections are of the most trifling extent. 

In no part of the Tertiary volcanic area of Britain can the characters of the lavas and 
the structure of the plateaux be so impressively seen as along the west side of Skye, 
north of Loch Bracadale. The precipices rise sheer out of the sea, to heights of some- 
times 1000 feet, and from base to summit every individual bed may be counted. As an 
illustration of the general succession of beds, I give here a diagrammatic view of the 




Fig. 23. — Section of the largest of Macleod's Maidens. 



largest of M'Leod's Maidens — the three wierd sea-stacks that rise so grandly in front of the 
storm-swept precipice at the mouth of Loch Bracadale. The height of the stack must be 
at least 150 feet (figs. 22 and 23). About ten distinct sheets of igneous rock can be counted 
in it, which gives an average thickness of 15 feet for the individual beds. It will be 
observed that there is a kind of alternation between the compact, prismatic basalts and the 
more earthy amygdaloids, but that the former are generally thickest.* These features, 

* A striking and illustrative contrast between the relative thickness of the beds of the two kinds of rock is supplied 
by the fine sections of this district. The amygdaloids range from perhaps 6 or 8 to 25 or 30 feet; but the prismatic 
basalts, while never so thin as the others, sometimes enormously exceed them in bulk. In the island of Wiay, for 
example, a bed of compact black basalt, with the confused starch-like grouping of columns, reaches a thickness of no 
less than 170 feet. Its bottom rests upon a red parting on the top of a dull greenish earthy amygdaloid. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 99 

which are repeated on cliff after cliff, may be considered typical for all the plateaux. 
Another characteristic point, well displayed here, is the intervening red parting between 
the successive beds. If the occurrence and thickness of this layer could be assumed as 
an indication of the relative lapse of time between the different flows of lava, it would 
furnish us with a rude kind of chronometer for estimating the proportionate duration of 
the intervals between the eruptions. It is to be noticed on the top both of the compact 
prismatic and of the earthy amygdaloidal sheets ; but is more frequent and generally 
thicker on the latter than on the former, which may only mean that the surfaces of the 
cellular lavas were more prone to subserial decay than those of the compact varieties. 
Nevertheless, I am disposed to attach some value to it, as an index of time. In the 
present instance, for example, it seems to me probable that the lavas in the lower half of 
M'Leod's Maiden, where the red layers are very prominent, were poured out at longer 
intervals than those that form the upper half. 

Another characteristic plateau-feature is admirably displayed in Skye — the flatness 
of the basalts and the continuity of their level terraces (though not of individual sheets) 
from cliff to cliff and hill-side to hill-side. This feature may be followed with almost 
tiresome monotony over the whole of the island, north of a line drawn from Loch Brittle 
to Loch Sligachan. Throughout that wide region, the regularity of the basalt-plateau is 
unbroken, except by minor protrusions of eruptive rock, which, so far as I have noticed, 
do not seriously affect the topography. But south of the line just indicated, the plateau 
undergoes the same remarkable change as in Rum, Ardnamurchan, and Mull. Portions 
of it which have survived indicate with sufficient clearness that it once spread south- 
wards and eastwards over the mountainous district, and even farther south into the low 
parts of the island. Its removal from that tract has been of the utmost value to 
geological research, for some of the subterranean aspects of volcanism have thereby been 
revealed, which would otherwise have remained buried under the thick cover of basalt. 
Denudation has likewise cut deeply into the eruptive bosses, and has carved out of them 
the groups of the Eed Hills and the Cuillins, to whose picturesque forms Skye owes so 
much of .its charm. 

In this, as in each of the other plateaux, there is no trace of any thickening out of 
the basalts towards a supposed central vent of eruption. The nearly level sheets may 
be followed up to the very edge of the great mountainous tract of eruptive rocks, 
retaining all the way their usual characters ; they do not become thicker there either 
collectively or individually, nor are they more abundantly interstratified with tuffs or 
volcanic conglomerates. On the contrary, their very base is exposed around the mountain 
ground, and the thickest interstratifications of fragmentary materials are found at a 
distance from that area. So far as regards the structure of the remaining part of the 
plateau, the eruption of the gabbros and granitoid rocks might apparently have taken 
place as well anywhere further north. 



100 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

§ 3. Vents of Eruption. 

In the approximate horizontality and regularly stratified arrangement of their 
component beds of lava, the plateaux of Britain resemble those of older Tertiary 
and still earlier date in other volcanic tracts, both in the Old and the New World, 
where the absence of any obvious vents from which the molten material flowed 
long presented a difficulty to geological students. I have stated that in no one in- 
stance have I been able to discover a trace of any central volcano, whence the sheets of 
basalt in the British plateaux could have proceeded. On the contrary, the uniformity 
of the beds in petrographical character, thickness, and persistent flatness point, I think, 
unmistakably to the occurrence not of a few great volcanoes, but of many minor vents 
breaking out one after another and shifting from district to district. Only by some such 
distribution of the foci of discharge can we account for the continuity and horizontality 
of the basalts that have gradually built up the plateaux. It is one of the most interesting- 
points in this volcanic history that, in spite of the enormous geological revolutions that 
have passed since they became extinct, the sites of many scattered vents can still be 
recognised. A far greater number must lie buried under the basalts, and of others the 
positions are concealed by the sea, which now covers so large an area of the old lava- 
fields. Nevertheless, partly on the surface of the plateaux, but still more on the 
surrounding tracts from which the basalts have been removed by denudation, the stumps 
of unmistakable vents of discharge stand out prominently amid the general wreck. 

Obviously it may be difficult to connect these vents directly with the plateau- 
lavas. On the one hand, those which project from the surface of the plateaux must, 
of course, be younger than the basalts through which they rise ; how much younger we 
cannot tell. They may possibly be later than any of the plateau-sheets ; they may even 
belong to a subsequent and waning condition of volcanic action. On the other hand, the 
vents which can now be traced outside of the present limits of the edges of the plateaux 
may, like those just mentioned, be younger than the basalt-sheets, or, on the contrary, 
they may be records of a period of eruptivity anterior to the emission of any of the rocks 
of the plateaux, and may have been deeply buried under a mass of basalt-beds 
subsequently removed. Positive demonstration is, from the nature of the case, impossible, 
unless we could find at the foot of the basalt-escarpment a volcanic vent immediately 
connected with some of the beds of the plateau above it.* When, however, we reflect 
that the vents which exist are precisely such as the structure of the plateaux would have 
led us to expect, we may not unreasonably look on them as part of the phenomena of 
this section of the volcanic period. Besides, in some cases, their connection with the 
rocks of the plateaux is as nearly proved as many facts in geology which nobody would 
now dispute. 

The most convenient classification of these vents is according to the nature of the 

* The instance of Carrick-a-raide, to be immediately referred to, is as near such a positive demonstration as could 
be looked for. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



101 



material that now fills them. They are either occupied by (a) some form of crystalline 
eruptive rock, or by (b) volcanic agglomerate. 

(a) Vents fitted with Dolerite, Basalt, &c. — These are by far the most numerous, and 
as this is what the composition of the plateaux would lead us to anticipate, the fact may 
be held to confirm the justice of the assumption that these vents were really sources for 
the plateau-lavas. They are perhaps most conspicuously visible in Antrim, both on the 
tableland and on the underlying rocks round its edges. The finest example in that 
district is undoubtedly furnished by the lofty eminence called Slemish, which rises above 
the surrounding basalt-terraces to a height of 1437 feet above the sea (fig. 24). It is 
elliptical in ground-plan, measuring some 4000 feet in length by 1000 in breadth. 
Seen from the north, it appears as a nearly perfect cone. The material of which it 
consists is a coarsely crystalline olivine-dolerite, presenting under the microscope a nearly 
noncrystalline aggregate, in which the lath-shaped felspars penetrate the augite, with 
abundant fresh olivine, and wedge-shaped patches of interstitial matter. The rock is 




Fig. 24. — Slemish, a Volcanic Neck or Vent on the Antrim Plateau, seen from the north. 



massive and amorphous, except that it is divided by parallel joints into large quadrangular 
blocks like a granitic rock, and wholly different from the character of the surrounding 
basalts. The latter, which possess the ordinary characters of the rocks of the plateaux, 
can be followed to within 80 yards of this neck, which rises steeply from them, but their 
actual junction with it can nowhere be seen, owing to the depth of talus. At the nearest 
point to which the two rocks are traceable, the basalts appear somewhat indurated, break 
with a peculiar splintery fracture, and weather with a white crust. These characters are 
still better shown on abundant fragments which may be picked up among the debris 
further up the slope. There can be no doubt, I think, that a ring of flinty basalt, 
differing considerably in texture from the usual aspect of that rock in the district, 
surrounds the neck. The meaning of this ring will be more clearly seen from the 
description of another example in Mull. About four miles to the north-east of Slemish, 
a smaller and less conspicuous neck rises out of the plateau-basalts. The rock of which 
it consists is less coarsely crystalline than that of Slemish, but its relations to the 

VOL. XXXV. PART 2. O 



102 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



.surrounding volcanic rocks is obviously the same. On the west side of Belfast Lough a 
boss of similar rock, about 1200 feet in diameter, rises at the very edge of the basalt 
escarpment into the eminence known as Carnmony Hill (fig. 25). On its northern side 
it presents along its wall a mass of interposed volcanic agglomerate.* Of the other 
doleritic necks scattered over the surface of the Antrim plateau, I will refer to only one 
which occurs on the hill slopes between Glenarm and Larne. It forms a prominence 
known as the Scawt Hill, and. consists of a boss of basalt, which, in rising through a vent 




Fig. 25. —Section of Volcanic Vent at Carnmony Hill (E. Hull). T, Lower basalt ; C, Cretaceous beds ; 

L, Lower Lias ; M, Triassic marls. 

in the plateau-sheets, has carried, up with it and converted into marble a large mass of 
chalk which is now exposed along its eastern wall (fig. 26). 

As examples of the similar necks which have been exposed by denudation outside the 
present limits of the plateau, I may allude to those which rise through the Cretaceous 
and other Secondary strata on the northern coast near Ballintoy. One of the most 
striking of these may be seen at Bendoo, where a plug of basalt, measuring about 1400 
feet in one diameter and 800 feet in another, rises through the Chalk, and alters it around 




Fig. 26. — Section of the east side of Scawt Hill, near Glenarm. a, bedded basalt ; b, mass of chalk ; c, basalt neck. 



the line of contact (fig. 27). Another remarkably picturesque example is to be seen near 
Cushendall, where a prominent doleritic cone rises out of the platform of Old Red Sand- 
stone, some distance to the north of the present edge of the volcanic escarpment. 

The greater coarseness of grain of the material filling these pipes, compared with that 
of the sheets in the terraces, is only what the very different conditions of cooling and 
consolidation would lead us to expect. There is no essential difference of composition 

* This neck was recognised by Du Noyer in 1868 as "one of the great pipes or feeders of the basaltic flows." 
See Prof. Hull, Explanation of Sheets 21, 28, and 29, Geol. Survey of Ireland (1876), p. 30. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



103 



between the two rocks ; but we find that where the erupted material has been poured 
out at the surface, it has assumed a finely crystalline texture, while, where it has slowly 
solidified within a volcanic pipe at some depth beneath the surface, and where con- 
sequently its component crystals have had more time for development, the resulting 
structure is much more largely crystalline, with a more complete development of the 
ophitic structure. 

In the island of Mull, another instance of the same kind of vent has been observed 
and described by Professor Judd. # It rises in the conspicuous hill, 'S Airde Beinne 
(Sarta Beinn), about two miles south-west from Tobermory, and consists of a coarsely 




»/Cr<y (w?v 



aba 
Fig. 27. — Section of Neck of Basalt, Bendoo, Ballintoy. aa, Chalk ; b, Neck. 

crystalline dolerite, which becomes rather finer in grain towards the outer margin (fig. 
28). No bedding or structure of any kind beyond jointing is perceptible in it. 
Examined in thin sections under the microscope, this rock is found to be another typical 
ophitic dolerite, consisting of lath-shaped felspars, embedded in augite masses, with here 
and there wedge-shaped portions of interstitial matter and grains of olivine. Dr Hatch 
observes that the felspars contain spherical inclusions of devitrified glass, filled with black 
granules and trichites and that, under a high power, the interstitial matter is seen to 
consist mainly of greenish-brown isotropic matter, in which are inclosed small crystals of 




Fig. 28.— Section of Volcanic Neck at 'S Airde Beinne, near Tobermory, Mull, aa, bedded basalts; bb, bedded basalts 

altered along the side of vent ; cc, dolerite. 

augite, skeleton-forms and microlites of felspar, sometimes in stellate aggregates, as well 
as club-shaped, cruciform, arrow-headed, and often crested microlites of magnetite. 

Towering prominently above the flat basalt sheets, this neck has an oval form, 
measuring about half a mile in length by a quarter of a mile in breadth. Its central 
portion, however, instead of rising into a rugged hill-top, as in all the other instances 
known to me, sinks into a deep hollow, which is filled with water, and reminds one of a 
true crater-lake. The middle of the neck is thus concealed from view, and we can only 
examine the hard prominent ring of dolerite that surrounds the tarn. That the material 

* Quart. Jour. Geol. Soc, xxx. (1874) p. 264. 



104 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

occupying the hollow must be softer than that of the ring is obvious, for great as is the 
temptation to look on this as a crater-lake, we must admit that what we now see is not 
the original surface, but has been exposed after the removal of possibly hundreds of feet 
of overlying material. The present lake-basin, whether or not it may represent a former 
crarer-lake, is undoubtedly due to erosion. Possibly some more easily removable 
agglomerate may here occupy the centre of the volcanic pipe. 

One of the most interesting features of this vent is to be found in its relation to the 
surrounding basalts. The marginal parts of the rock along the line of contact are much 
finer in grain than the rest, and have obviously cooled more rapidly. The contrast 
between them and the ordinary dolerite of the centre, however, cannot be properly 
understood, except in thin sections under the microscope. Dr Hatch observes that, in 
place of the structure above described, the marginal parts show an absence of the ophitic 
grouping except in small isolated patches. Instead of occurring in large grains or plates 
enveloping the felspars, the augite is found in numerous small roundish grains, together 
with grains of magnetite, in equal abundance and of similar size. The felspars are 
spreckled over with opaque particles ; olivine was not detected. 

For miles around the vent, the plateau-rocks are of the usual type — black, compact, 
sometimes amygdaloidal, alternating with more coarsely crystalline decomposing bands, 
the separation between different sheets being often marked by the ordinary red ferruginous 
partings. But around the margin of the neck, they have undergone a remarkable meta- 
morphism. The portions of them which adhere to the outer wall of the neck have lost 
their distinct bedding, and have been, as it were, welded together into an indurated 
compact, black to dull-grey rock, so shattery and jointed that fresh hand-specimens, 
three or four inches in length, are not easily obtainable. Especially marked is one set of 
joints which, running approximately parallel, cause the rock to split into plates or slabs. 
These joints are sometimes curved. . Yet, in spite of the alteration from its normal 
character, the basalt retains in places some of its more usual external features, such, for 
instance, as its amygdaloidal structure, the amygdules consisting of calcite, finely acicular 
mesotype, and other minerals. 

Examined under the microscope, this altered basalt presents " a confused aggregate of 
colourless microlites (felspar V) and innumerable minute granules of magnetite, these two 
constituents being very unequally distributed. Sometimes the colourless portions pre- 
ponderate, in other places the opaque granules are heaped together in black patches, 
which may possibly mark the position of fused augites " (Dr Hatch). 

In the zone of contact-metamorphism around some of the volcanic pipes in the 
plateaux, we see changes analogous to, but less developed than, those which have been 
superinduced on so large a scale round the great eruptive bosses of gabbro, granophyre, 
&c, that have broken up the terraced basalts along the west coast of Scotland. I shall 
accordingly return to this subject in connection with the phenomena presented by these 
younger rocks. 

(b) Vents filled ivith Agglomerate. — Though much less frequent than the necks of 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



105 



dolerite, those filled with fragmentary materials bring before us, perhaps more vividly, 
the volcanic conditions in which they were formed. The agglomerate is generally 
exceedingly coarse, and without any trace of structure. Blocks of all sizes up to masses 
some yards in length, and of the most diversified materials, both volcanic and non- volcanic, 
are dispersed confusedly through a granular paste of similar miscellaneous composition. 

One of the most instructive examples has been already alluded to as occurring at the 
island of Carrick-a-raide, on the north coast of Antrim. It forms that island, and a 
portion of the opposite mainland. Its visible mass is about 1000 feet in diameter, but 
the boundaries, except on the land side, are concealed by the sea. The material filling 
up this vent is a coarse agglomerate, in which blocks and bombs of basalt, with pieces of 
chalk and flint, are stuck at all angles in a dull dirty-green granular tuff. Some large 
and small intrusions of basalt rise through it. Owing partly to these intrusions, and 
partly to the grass-covered slope that separates it from the line of cliff, the actual contact 
of this neck with the volcanic beds of the escarpment cannot be seen. I have no doubt, 
however, that the tuff, which has already been referred to as so conspicuous a member of 




Fig. 29. — Diagram to show the probable relation of the Neck at Carrick-a-raide, Antrim, to an adjacent group of Tuffs, aa, 
Chalk ; bb, Lower group of bedded basalts ; c, Vent of Carrick-a-raide, filled with coarse volcanic agglomerate ; dd, bedded 
tuffs ; ee, large veins of basalt traversing the agglomerate ; ff, zone of tuffs and pisolitic iron ore ; gg, Upper group of 
bedded basalts. 



the series here, was discharged from this vent.* The materials are as usual coarser in 
the pipe than beyond it, but the finer portion or matrix of the agglomerate is similar to 
many bands of the tuff. The structure of the locality may be diagrammatically repre- 
sented as in fig. 29. The bedded tuff is thickest in the neighbourhood of the vent, and 
gradually dies away on either side of it. 

But another important inference may be drawn from this locality. I have already 
pointed out that the lower basalts here reach their minimum thickness. Their basement 
beds thin away towards the vent as markedly as the tuff thickens. Obviously they 
cannot have proceeded from that point of eruption. Yet, that they had begun to be poured 
out before the discharge of the tuff, is shown by their underlying as well as overlying that 
rock, though westward, owing to the thinning away of the undermost basalts, the tuff 
comes to lie directly on the Chalk. Hence, we may legitimately infer the existence of one 
or more other vents in the neighbourhood that supplied the sheets of the lower basalts. 

In the promontory of Ardnamurchan, where the basalt-plateau has been so obscured 

* See Explanation of Sheets 7 and 8, Geol. Survey of Ireland (1888), p. 31. 



106 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

by later intrusions of crystalline rocks and reduced to such a fragmentary condition by 
denudation, some interesting examples of agglomerate necks have been laid bare. The 
largest of these occurs on the north shore at Faskadale. Cut open by the sea for more 
than a quarter of a mile, this neck is seen to be filled with a coarse agglomerate, composed 
mainly of basalt-blocks and debris, but crowded also with angular and subangular pieces 
of different close-grained felsitic and porphyritic rocks belonging to the acid series to be 
afterwards described.* Some of these stones exhibit a very perfect flow-structure, and 
closely resemble certain fine-grained flinty intrusive rocks in Mull, to which allusion will 
subsequently be made. The matrix of the agglomerate is of the usual dull dirty-green 
colour, but is so intensely indurated that on a fresh fracture it can hardly be distinguished 
from some of the crystalline rocks of the locality. The neck is pierced in all directions 
with dykes and veins of basalt, dolerite, gabbro, and felsitic rocks. Similar intrusions 
continue and increase in numbers further west until the cliffs become a labyrinth of dykes 
and veins running through a mass of rock which appears to consist mainly of dull dolerites 
and fine gabbros. Though the relations of this vent to the plateau-basalts are not quite 
plain, the agglomerate seemed to me to rise out of these rocks. At least the basalts extend 
from Achateny to Faskadale, but, as they are followed westwards, they are more and 
more invaded by eruptive sheets, and assume the indurated character to which I have 
already referred. 

On the south side of the peninsula of Ardnamurchan, another neck, noticed by 
Professor Judd, rises into the bold headland of Maclean's Nose, at the mouth of Loch 
Sunart, and affords better evidence of its relation to the bedded basalts. It measures 
about 1000 yards in length by 300 in breadth, and its summit rises more than 900 feet 
above the sea, which washes the base of its southern front. It is filled with an agglo- 
merate even coarser than that on the northern coast. The blocks are of all sizes, up to 
eight or ten feet in diameter. By far the largest proportion of them consists of varieties 
of basalt, slaggy and vesicular structures being especially conspicuous. There are also 
large blocks of different porphyries and felsitic rocks like those just referred to, a 
porphyry with felspar crystals two inches long being particularly abundant. All the 
stones are more or less rounded, and are wrapped up in a dull-green compact matrix of 
basalt-debris. There is no stratification or structure of any kind in the mass. Numerous 
dykes or veins, some of basalt, others of a porphyry, resembling that of Craignure, in 
Mull, traverse the agglomerate. 

The position of this vent, with reference to the surrounding rocks, will be best 
understood from the map (Plate L), and from the subjoined section (fig. 30). On the 

* One of these felsites when viewed under a high magnifying power is seen to present an abundant development of 
exceedingly minute micropegmatite arranged in patches and streaks parallel with the lines of fluxion structure in the 
general cryptocrystalline ground mass. The close relationship between the felsites, quartz-porphyries, and grano- 
phyres will be afterwards pointed out in the description of the acid rocks.' It is remarkable that, though these rock* 
occur abundantly in fragments in the volcanic necks and agglomerates of the plateaux, not a single instance has been 
observed of their intercalation as contemporaneous sheets among the basic lavas. An analogous case of the interstratifi- 
cation of felsitic tuffs among basic lavas occurs in the volcanic series of the Old Red Sandstone of central Scotland. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



107 



eastern side, the agglomerate can be seen to abut against the truncated ends of the flat 
beds of the plateau-basalts, which are of the usual bedded compact and amygdaloidal 
character. There can be no doubt, therefore, that the vent has been opened through these 
basalts. But it will be observed that the latter belong to the lower part of the volcanic 
series. These lowest sheets are exposed on the slope, resting upon yellowish and spotted 
grey sandstone, with seams of jet and a reddish breccia, which, lying in hollows of the 
quartzites, quartz-schists, and mica-schists, form no doubt the local base of the Jurassic 
rocks of the district. Hence, the vent, though younger than the older sheets of the 
plateau, may quite well be contemporaneous with some of the later sheets. 

An interesting feature at this locality is the peculiar grouping of some of the large 
dykes in the area around the agglomerate. They run in the direction of the vent, and 
one or other of them may represent the fissure or fissures on which the volcanic orifice 
was blown open to the surface. Another notable element in the geological structure of 
the ground is the vast amount of intrusive material, both in dykes and sheets, which has 
been erupted. The intrusive sheets of Ben Hiant form the most prominent eminence in 




d' d c d a 

Fig. 30. — Section of agglomerate Neck at Maclean's Nose, Ardnamurchan. aa, Quartzites and schists; b, bedded basalts 
lying partly on the schists and partly on patches of Jurassic sandstones that occupy hollows of the older crystalline 
rocks ; c, agglomerate ; dd, dykes and veins traversing the agglomerate ; e, dolerite sheets of Ben Hiant. 



this part of Ardnamurchan. Reserving them for description in a later part of this 
memoir, I will only remark here that they partly overlie the agglomerate, and are there- 
fore to some extent at least younger than the vent. They belong to that late stage in 
the history of the basalt-plateaux when the molten material, no longer getting ready 
egress to the surface, forced its way among the rocks about the base of the bedded basalts, 
and more especially on the sites of older vents, which were doubtless weak places, where 
it could more easily find relief. 

By far the largest mass of agglomerate in any of the Tertiary volcanic areas is that 
which occurs on the north side of the main valley of Strath, in Skye.* Unfortunately, 
it has been so seriously invaded by the eruptive rocks of the group of the Red Hills, that 

* This extensive mass was not separated from the " syenite " of the Red Hills by Macculloch. Von Oeynhausen 
and Von Dechen noticed it as a conglomerate with quartz pebbles, but did not realise its volcanic nature (Karsten's 
Archiv, i. p. 90). In my map of Strath (Quart. Jour. Geol. Soc, xiv. plate i.) I distinguished it from the rock of the 
Red Hills, but no name for it appears in the legend of the map, nor is it referred to in the text. Its character as a true 
volcanic agglomerate was recognised by Professor Judd, Op. cit., p. 255. See Plate II. of the present memoir. 



108 DR OEIRIE ON THE HISTORY OF VOLCANIC ACTION 

its original dimensions and its relations to the surrounding rocks, especially to the bedded 
basalts, are much obscured. It can be followed continuously from the lower end of Loch 
Kilchrist along the southern slopes of Beinn Dearg Bheag round to the western roots of 
Beinn Dearg Mhor — a distance of more than two miles in a straight line, and from 
Kilbride to the flank of Beinn na Caillich above Coire-chat-acban — a direct distance of 
two miles and a quarter. A similar rock, possibly a portion of the same mass, appears in 
Creagan Dubha, on the north side of the Red Hills. If the whole of this agglomerate 
forms part of one originally continuous mass, the vent must have been upwards of two 
miles in diameter. There may, however, have been two or three closely adjacent vents. 
The Beinn na Caillich patch, for example, appears to belong to a different area, and that 
of Creagan Dubha may also be distinct. But there seems no reason to doubt that the 
mass which forms Cnoc nam Fitheach, and all the long declivity on the southern flank of 
Beinn Dearg Bheag, occupies part of the site of a single volcanic funnel, which was 
almost two miles in diameter. 

This agglomerate is a coarse tumultuous assembage of blocks and bombs, embedded 
in the usual dull, dirty-green matrix. Among the stones, scoriaceous, vesicular, and 
amygdaloidal basalts are specially abundant ; also pieces of various quartz-porphyries, 
among which a black felsite like that of Mull may often be recognised. In some places, 
large masses of altered Lower Silurian limestone and quartzite are included ; in others, 
pieces of yellow sandstone and dark shale (Jurassic). The rock is wholly without strati- 
fication or structure of any kind. On the north-west side of Loch Kilchrist, indeed, it 
weathers into large tabular forms, the parallel surfaces of which dip to S.W. ; but this is 
probably due only to jointing. Here and there, dykes of basalt cut the rock in a general 
north-westerly direction, but their number is remarkably small when compared with the 
prodigious quantity of them in the limestone at the bottom and opposite side of the 
valley, some of which may possibly mark the fissure of the vent. More abundant and 
extensive are the masses of granophyre that rise more particularly along the outer margin 
of the vent. These are doubtless connected with the great boss that forms the Red 
Hills, of which further details will be given in a subsequent section of the paper. 

The important question of the relation of this huge vent to the plateau-basalts does 
not admit of satisfactory treatment, owing to destruction of the evidence by the 
intrusion of the granophyre and likewise to enormous denudation. Nevertheless, some 
traces still remain to indicate that the basalts once stretched over the site of the vent, 
which probably rose through them. Looking westward from the flanks of Beinn Dearg 
Bheag to the other side of Loch Slapin, the geologist sees the bold basalt-escarpment of 
Strathaird presenting its truncated beds to him at a distance of only two miles. That 
these beds were once prolonged eastwards beyond their present limits is obvious, and that 
they stretched at least over these two intervening miles can hardly be doubted. But we 
can still detect relics of them on the flanks of Beinn Dearg. As we follow the agglomerate 
round the margin of the granophyre that mounts steeply from it, we lose it here and 
there under beds of amygdaloidal basalt. The rocks next the great eruptive mass of the 




DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 109 

mountain are so indurated and shattered that it is difficult to separate them from each 
other and determine their relative positions. But, so far as I could ascertain, these 
basalts are fragments of beds that overlie the agglomerate (fig. 31). This is not the only- 
place along the flanks of the Ked Hills where portions of the 
bedded basalts have survived. Other localities will be sub- 
sequently alluded to. 

The great vent of Strath has been drilled through the 
Lower Silurian limestone, and as the result of protracted 
denudation it now towers steeply five or six hundred feet 
above that formation on the floor of the valley. Of the 
material discharged_ from it over the surrounding country no Fig- 31.— Diagram to show the 

TTT . „ „ , „ probable relations of the rocks 

certain trace now remains. We may inter irom the nature 01 n the southern flank of Beinn 
the rock which fills it that towards the end, if not from the Dear g Bhea s- «> agglomerate ; 

, .. . . b, amygdaloidal and compact 

beginning ot its activity, its discharges consisted mainly 01 basalt-rocks ; c, granophyre. 
dust and stones. A crater, of which the pipe was two miles in 

diameter, must surely have sent its fragmentary materials far and wide over the sur- 
rounding region. But on the bare platform of older rocks to the south not a vestige 
of these erupted materials can now be found. Westward the escarpment of Strathaird 
remains to assure us that no thick showers of ashes fell at even so short a distance as two 
miles, either before or during the outpouring of the successive basalt sheets still remaining 
there. We may therefore conclude with some confidence that here, as at Ardnamurchan, 
the vent must be younger than at least the older parts of the basalt-plateau. Unfortun- 
ately the uprise of the large bosses of granophyre that stretch from the Eed Hills to Loch 
Sligachan has entirely destroyed the vent and its connections in that direction. There 
is no certain proof that any molten rock ever issued from this orifice, unless we suppose 
the fragmentary patches of amygdaloid on the southern flank of Beinn Dearg Bheag to 
be portions of flows that proceeded from this centre of eruption. I have little doubt that 
the basalt-plateau which still remains in Strathaird formerly extended eastwards over 
Strath and northwards across the site of the Red Hills and Cuillins, joining on to 
the continuous tableland north of Lochs Brittle and Sligachan. How much of the 
plateau had been built up here before the outburst of the vent can hardly be conjectured. 
The agglomerate may possibly, of course, belong to the very latest period of the plateau- 
eruptions, or even to a later phase of Tertia^ volcanic history. The impression, however, 
made on my mind by a careful study of the evidence from this and the other districts is 
that the necks of agglomerate, like those of dolerite and basalt, really belong to different 
epochs of the plateau period ; that they mark for us some of the vents from which the 
materials of the plateaux were emitted. 

The example of Car rick- a-raide is peculiarly suggestive when we regard it in 
connection with the great Strath vent. Already the progress of denudation has removed 
at least half of the layer of dust and stones which, thrown out from that little orifice, fell 
over the bare chalk-wolds and black basalt-fields of Antrim. The neck that marks the 

VOL. XXXV. PART 2. P 



110 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

position of the volcanic funnel has been largely cut away by the waves, and is almost 
entirely isolated among them. But the inarch of destruction has been greater in Skye. 
The connection between the vent and the materials ejected from it has been entirely 
removed, and we can only guess from the size of the remaining neck what may have been 
the area covered by the discharges from this largest of all the volcanic cones of the Inner 
Hebrides. 

In bringing this part of my subject to a close, I would repeat that the distinctive 
characters of the basalt-plateaux lead us to seek the modern analogies to these volcanic 
phenomena, not in large central cones discharging streams of lava in different directions 
like Vesuvius or Etna, but in those basalt-regions where the lavas have issued from 
innumerable minor and sometimes almost imperceptible vents.* I have already referred 
to a journey made by me in 1879 through some of the vast basalt-fields of Western 
America, and to the light which I thereby gained on the history of the youngest volcanic 
tracts of Britain. The basalt of Idaho stretches out as a vast and apparently limitless 
plain. Along its northern boundary, this sea of black lava runs up the valleys and round 
the promontories of the older trachytic hills, with almost the flatness of a sheet of water. 
It has been deeply trenched, however, by the streams that wind across it, and especially 
by the Snake River, which has cut out a gorge some 700 feet deep, on the walls of which 
the successive beds of basalt lie horizontally one upon another, winding along the curving 
face of the precipice exactly as those of Antrim and the Inner Hebrides do along their 
sea- worn escarpments. Here and there, a low cinder-cone on the surface of the plain 
marks the site of a late outflow. One is struck, also, with the singular absence of tuffs 
and volcanic conglomerates. The basalts appear to have flowed out stream after stream 
with few fragmentary discharges. 

These characteristic features of one distinctive type of volcanic action have been 
repeated over a vast region, or rather a whole series of regions, in Western America, the 
united area of which must equal that of a considerable part of Europe. From Idaho, the 
basalt-fields may be followed southwards interruptedly into Utah and Nevada, and across 
the great plateau-country of the canons into Arizona and New Mexico, northwards into 
Montana, and westwards into Oregon. The tract which has as yet been most carefully 
traversed and described is probably that of the high plateaux of Utah and Arizona. 
Thus on the Uinkaret plateau, which measures some 45 to 50 miles in length by 8 to 12 
in breadth, a thick sheet of basalt has been spread consisting of many successive flows. 

* In this connection I may again refer to Hopkins's Researches in Physical Geology, where the conditions of the prob- 
lem here discussed have been distinctly realised. Speaking of the ejection of lava from a number of fissures, he remarks 
that the imperfect fluidity of the melted material " would seem to require a number of points or lines of ejection as a 
necessary condition." " If there were only a single centre of eruption, a bed of such matter approximating to uniformity 
of thickness, could only be produced on a surface of a conical form." " Where no such tendency to this conical structure 
can be traced, it would probably be in vain to look for any single centre of eruption. On the supposition, too, of 
ejection through continued fissures, or from a number of points, that minor unevenness of surface which must probably 
have existed under all circumstances during the formation of the earth's crust, would not necessarily destroy the 
continuity of a comparatively thin extensive bed of the ejected matter, in the same degree in which it would inevitably 
produce that effect in the case of central ejection " (Cambridge P\il. Trans., vi. (1835), p. 71). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. Ill 

Between 160 and 170 separate cones have been counted on this area, most of them quite 
small, mere low mounds of scoriae, though a few reach a height of 700 or 800 feet, with a 
diameter of a mile. From three to seven or eight may be found in a row, as if springing 
from a single line of fissure. But generally the grouping is quite irregular."" My friend 
Captain C. E. Dutton, from whose admirable memoir these details are quoted, remarks 
further that among the Utah plateaux no trace of a cone is to be found at or near some 
of the most recent basalt-fields, and that the most extensive outpours are most frequently 
without cones. " The lavas," he adds, " appear to have reached the surface and over- 
flowed like water from a spring, spreading out immediately and deluging a broad surface 
around the orifice." t The deep gorges cut by the rivers through these thick accumulations 
of horizontal or nearly horizontal basalts, have here and there revealed the parallel dykes 
that traverse the rocks, and in at least one case have shown the dyke running for half a 
mile up a cliff and actually communicating with a crater of scoriae at the top. J Again, 
in New Mexico, Captain Dutton noticed vast tracts of younger basalt, about which " a 
striking fact is the entire absence of all distinguishable traces of the vents from which 
they came. Some of them, however, indicate unmistakably their sources in small 
depressed cones of very flat profiles. No fragmental ejecta (scoriae, lapilli, &c.) have been 
found in connection with these young eruptions." § Such I believe to have been the 
general conditions under which the basalts of the Tertiary plateaux of the British Isles 
were also erupted. 

§ 4. Intrusive Sheets or Sills of the Plateaux. 

There is one further part of the structure of the basalt-plateaux of which some 
account must now be given. In a former paper, I have shown that at different parts of 
the basalt series, but especially at their base and among the stratified rocks underneath 
them, sheets of basalt and dolerite occur which, though lying parallel with the strati- 
fication of the volcanic series, are not truly bedded masses, but are intrusive sills, 
and therefore of younger date than the rocks between which they lie. || The non- 
recognition of their intrusive and subsequent nature led to these sheets being 
regarded as proofs of the intercalation of volcanic beds in the Jurassic series of western 
Scotland. There is, however, not the least trace of the true interstratification of a 
volcanic band in any part of that series, every apparent example being due to the 
way in which intrusive sheets simulate the characters of contemporaneous flows. 

If such sheets had been met with only at one or two localities, we might regard them 
as due to some mere local accident of structure in the overlying crust through which the 
erupted material had to make its way. But when we find them everywhere, from the 

* C. E. Dutton, "Tertiary History of the Grand Canon District," U.S. Geol. Swrvey (1882), p. 104. 
t C. E. Dutton, " Geology of the High Plateaux of Utah," U.S. Geol. Survey of the Rocky Mountain Region (1880), 
pp. 198, 200. See also pp. 232, 234, 276 of the same Monograph for additional examples. 
J Tertiary History of the Grand Canon, &c, p. 95. 
§ Nature, xxxi. (1884) p. 89. 
|| Quart. Jour. Geol. Soc, xxvii. (1871) p. 296. 



112 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

far headlands of Skye to those of Antrim, it is obvious that they must be due to some 
general cause, and that they contain the record of a special period or phase in the building 
up of the volcanic tablelands. I will first describe some typical examples of them from 
different districts, and then discuss their probable relations with the other portions of 
the plateaux. 

First to be examined, and now most familiar to geologists, are the remarkable sheets 
that underlie the plateau of Antrim, and project at various parts of the picturesque 
line of coast from Portrush to Fair Head. From the shore at Portrush came the evidence 
that was supposed to prove basalt to be a rock of aqueous origin, inasmuch as shells were 
obtained there from what was believed to be undoubtedly basalt. The long controversy 
to which this supposed discovery gave rise is one of the most curious in the history of 
geology.* Fellows of this Society have cause to remember with pleasure that it was one 
of their predecessors, the illustrious Playfair, who showed the pretended basalt to be in 
reality highly indurated shale, and hence that, instead of furnishing proof of the aqueous 
formation of basalt, the Portrush sections only contributed another strong confirmation of 
the Huttonian theory, which claimed basalt to be a rock of igneous origin. 

It is now well known that the rock which yielded the fossils is a Liassic shale, that 
it is traversed by several sheets of eruptive rock, and that by contact-metamorphism it 
has been changed into a highly indurated substance, breaking with a splintery, conchoidal 
fracture, but still retaining its ammonites and other fossils. The eruptive material is a 
coarse, distinctly crystalline dolerite, in some parts of which the augite with its penetrating 
lath-shaped crystals of plagioclase is remarkably fresh, while the olivine has begun to 
show the serpentinous change along its cracks, t This rock has been thrust along the 
bedding planes of the shales, but also breaks across them, and occurs in several sheets, 
though these may all be portions of one subterranean mass. Some of the sheets are only 
a few inches thick, and might at first be mistaken for sedimentary alternations in the 
shale. But their mode of weathering soon enables the observer readily to distinguish 
them. It is to be noticed that these thin layers of eruptive material assume a fine grain, 
and resemble the ordinary dykes of the district. This closeness of texture, as Griffith 
long ago pointed out, J is also to be noticed along the marginal portions of the thicker 
sheets, where they lie upon or are covered by the shales. But away from the surfaces of 
contact, the rock assumes a coarser grain, insomuch that in its thickest mass it presents 
crystals measuring sometimes an inch in length, and then externally resembles a gabbro. 
A more curious structure is shown in one of these coarsely crystalline portions by the 
occurrence of a band a few inches broad which is strongly amygdaloidal, the cells, some- 
times three inches or more in diameter, being filled with zeolites. § The general dip of 

* For an excellent summary of it and an epitome of the descriptions of the Portrush section, see the Report on the 
Geology of Londonderry, &c, by J. E. Portlock (1843), p. 37. 

t Dr F. Hatch, Explanation of Sheets 7 and 8, Geol. Survey of Ireland, p. 40. 

X "Address to Geological Society of Dublin, 1835," p. 13, Jour. Geol. Soc. Dublin, vol. i. The varieties of the 
Portrush rock were described by the late Dr Oldham, in Portlock's Report on the Geology of Londonderry, p. 150; see 
also the same work for Portlock's own remarks, p. 97. 

§ For a list of the minerals in this rock, see Oldham, op. tit., p. 151. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



113 



the shales and of the intrusive sheets which have been injected between them is towards 
the east. From underneath them a thick mass of dolerite rises up to form the long 
promontory that here projects northwards from the coast-line, and is prolonged seawards 
in the chain of the Skerries. 

An interesting feature of the Portrush sections is the clear way in which they exhibit 
the phenomena of segregation-veins — so characteristic of the thicker and more coarsely 
crystalline intrusive sheets. These veins or seams differ from the rest of the rock mainly 
in the much larger size and more definitely crystalline form of their component minerals. 
Though sharply defined, when looked at from a little distance, they are found on closer 
inspection to shade into the surrounding rock b}^ a complete interlacing of crystals. 
On the shore, they can be seen to lie on the whole parallel with the bedding of the sheets 
in which they occur, but without rigidly following it, since they undulate and even 
ramify. A good section across their dip has been exposed in a quarry near the end of 
the promontory, and shows that they are considerably less regular than the plan of their 




Fig. 32.— View of Segregation Veins in dolerite of an Intrusive Sheet, Portrush, Antrim. 

outcrop on the shore would have led us to anticipate. The accompanying drawing (fig. 
32) represents the veins laid bare on a face of rock 9 feet in length by 5 feet in height. 
It will be seen that while there is a general tendency to conform to the dip-slope, which, 
is here from right to left, the seams or layers unite into a large rudely bedded mass, 
which sends out processes across the bedding. The peculiar aggregation of minerals 
which distinguishes such segregation veins is perhaps best seen at Fair Head, and I 
reserve for the description of that locality what I have to say on the subject, only 
remarking with regard to the Portrush rock that the felspar shows a disposition to collect 
in the centre of the veins with the augite and the other dark minerals at the outer 
margins. 

The contact-metamorphism at this locality is of more historical interest in connection 
with the progress of geological theory than of scientific importance. It consists mainly 
in an intense induration of the argillaceous strata. These pass here from their usual 



114 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



condition of fissile, laminar, dull, dark shales into an exceedingly compact, black, flinty 
substance, which in its fracture, colour and hardness reminds one of Lydian stone. Yet 
the ammonites and other organic remains have not been destroyed. They are preserved 
in pyrites. 

Of all the examples of intrusive sheets of Tertiary age in Britain there is none more 
imposing than that of the noble range of precipices which form the promontory of 
Fair Head. Leaving out of account the minor masses of eruptive rock which occur 
underneath it, we find the main sheet to extend along the coast for nearly four miles, 
to rise to a height of 636 feet above the sea, and to attain a maximum thickness of 250 
feet. This enormous bed dies out rapidly both to the east and west, and seems also to 
thin away inland. Seen from the north, it stands upon a talus of blocks as a sheer 



?VT~vTf'f \ .hi \\\\ 









-^ -"l ^<r — - — ^ x ^ ^ \ ,v 



, V X^^^=^^^ 




Fig. 33. — View of Fair Head from the East, showing the main upper intrusive sheet and a thinner sheet cropping out along 

the talus slope. 

vertical wall, 250 feet high, and the rude prisms into which it is divided are continuous 
from top to bottom (fig. 33). So regular is this prismatic structure, and so much does 
it recall the more perfect columnar grouping of the basalts, that at a little distance we 
can hardly realise the true scale of the structure. It is only when we stand at the base 
of the cliff or scramble down its one accessible gully, the " Grey Man's Path," that we 
appreciate how long and thick each of the prisms actually is. 

The rock composing this magnificent sheet is a coarsely crystalline, ophitic, olivine- 
dolerite.* The same diminution of the component crystals, which is so marked along the 

* Professor Judd has described what he calls a " glomero-porphyritic structure" in this rock (Quart. Jour. Geol. 
.W., xlii. (1886) p. 71). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 115 

margins of the eruptive masses at Portrush, is strikingly exhibited at Fair Head. For 
about 18 or 20 inches upward from the bottom, where the bed rests on the black, 
Carboniferous shales, the dolerite is dark and finely crystalline, weathering spheroidally 
in the usual manner. But immediately above that bottom layer of closer grain the 
normal coarsely crystalline texture rapidly supervenes. A similar closeness of grain 
is observable at the surfaces of contact where the sheet splits up on its western 
border. 

Nowhere, so far as I know, can the phenomena of segregation veins be so instructively 
studied as along the abundant exposures of this great sheet. The veins are most conspicu- 
ous where the rock occurs in thickest mass. They vary up to three or four feet in thick- 
ness, and, as at Portrush and elsewhere, lie on the whole parallel to the upper and under 
surfaces of the sheet. An erroneous impression may be conveyed by the term " veins " 
applied to them. They are quite as much layers, parallel on the whole with the bedding 
of the sheet, yet not adhering rigidly to one plane, but passing across here and there 
from one horizon to another. That they are not due to any subsequent protrusion of 
younger material through the main sheet is made manifest by the thorough interlocking 
of their component crystals with those of the body of the rock in which they lie. They 
consist of an exceedingly coarse aggregate of crystals, or rather of crystalline lumps of 
the minerals that constitute the general mass of the rock, the felspar and augite showing 
the ophitic intergrowth of the main rock, but on a far larger scale. Some of the pieces 
of augite measure two inches or more in diameter. 

This great Fair Head sheet lies upon Carboniferous strata, but that it is to be classed 
with the Tertiary volcanic series is, I think, demonstrated by its relations to the Chalk at 
its eastern end. It has there broken through that rock, and converted it for a short 
distance into a white, granular marble. But it is at the western side that the most 
interesting sections occur to show the truly intrusive nature of the mass. The rock there 
splits up into about a dozen sheets, which, keeping generally parallel with each other, have 
forced their way between and partly across the bedding planes of the Carboniferous 
shales (fig. 34). In this way the huge, unbroken mass, 250 feet thick, subdivides itself 
and disappears in a few hundred yards, though it continues a little further inland, and 
approaches the shore again half a mile to the south-west. Further evidence of the 
intrusive nature of this rock may be observed along the base of the precipice, where at 
least one sheet 70 feet thick diverges from the main mass and runs eastwards between 
the Carboniferous shales (fig. 33). At the contact with the eruptive rock the shales are 
everywhere much indurated. 

All through the Inner Hebrides the base of the basalt series generally presents 
abundant examples of intrusive sheets. I have already alluded to this fact as an 
explanation of the conclusion to which geologists were led, that in Skye and elsewhere 
the basalts are interstratified with the Jurassic rocks, and are consequently of Jurassic age. 
It was Macculloch who first described and figured in detail these proofs of intrusion. 
His well-known sections in plate xvii. of the illustrations of his work on the Western 



116 



DR OEIKIE ON THE HISTORY OF VOLCANIC ACTION 



Islands have been repeatedly copied, and have served as typical figures of intrusive 
igneous rocks. 

Though none of the examples in the Inner Hebrides attain the dimensions of the Fair 
Head sheet, still they present a much greater variety of rock and of geological structure 
than is to be found in Antrim. I have already referred to the base of the thick, overlying, 
basalt-plateaux in Scotland, as a horizon along which a prodigious quantity of eruptive 
material has subsequently been injected. Part of this material consists of basic rocks 
in the form of dykes, veins, or sills ; part of it is included in the acid group, and 
comprises veins, sheets, and bosses of granitoid, felsitic, rhyolitic, trachytic, and pitch- 
stone rocks. With regard to the basic sheets (dolerites, basalts, &c.) which occur on this 
horizon, I would remark that while in western Scotland the Antrim type is also found, 
the vast majority of the sheets belongs to a quite distinct type. For the sake of 
continuity, I may first describe some examples of the occurrence of thick, coarsely 
crystalline, rapidly diminishing sills like those of the north coast of Antrim. 




Fig. 34. — Section at Farragandoo Cliff, west end of Fair Head, showing the rapid splitting up and dying out of an Intrusive 
Sheet, a, Carboniferous sandstone ; b, Carboniferous shale ; c, intrusive sheet. 



On the coast of Skye, between Lochs Slapin and Eishort, the prominent headland of 
Suisnish has long been known to geologists from the section of it given by Macculloch 
as an instance of the connection between overlying rocks and dykes. I have already 
alluded to it in that relation, and refer to it again as an example of one of the thicker 
intrusive sheets of the Inner Hebrides. Denudation has proceeded so far in that district 
of Skye that the whole of the volcanic plateau has been stripped off, and we have only 
some of the underlying sills left, with the platform of older rocks between which and the 
vanished basalts they were injected. Most of these sills consist of granophyres belonging 
to the acid group of rocks to be afterwards described. But among them there occur true 
dolerite sheets not infrequently interposed between the granophyres and the subjacent 
Lias, and sometimes even intercalated in the former rock. Though at first sight it might 
be thought that these sills had insinuated themselves after the eruption of the granophyre, 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 117 

and there are instances where this cannot be shown not to be the case, I have obtained 
so many proofs of the invasion of the basic by the acid rock that I have no doubt the 
former is as a general rule the older of the two. The Suisnish headland exhibits the 
structure represented in fig. 14. For about 300 feet above the sea-level the steep grassy 
slope shows outcrops of the dark, sandy shales and yellowish brown, shaly sandstones 
of the Lias which form the range of cliffs to the eastward. These gently inclined 
strata are cut through by many vertical basalt-dykes, some of which intersect each other, 
but among which by far the largest is the mass shown in the figure. This broad dyke 
consists of a dolerite, the largely crystalline texture of which marks it off at once from 
the others, which are of the usual dark, heavy, fine-grained type, with an occasional 
andesitic and porphyritic variety. Traced up from the sea-margin, the dyke loses itself 
in a talus of blocks from the cliff above, so that its actual junction with the mural front 
of the sill cannot be seen. But that it joins that mass, with which it agrees in petro- 
graphical characters, hardly admits of question. The cliff consists of a thick sheet of 
coarsely crystalline dolerite (c in fig. 14), which in its general aspect at once recalls the rock 
of Fair Head. It varies considerably in texture, some parts of the mass are exceedingly 
coarse, like the Skye gabbros, and present a fibrous structure in their augite resembling 
that of the diallage in these rocks ; other portions assume the compactness of basalt. A 
specimen of medium grain under the microscope shows the typical ophitic structure so 
generally found among the dolerites both of the plateaux and of the intrusive sheets. 
This sill must be about 200 feet thick, and like the rock at Fair Head is traversed from 
top to bottom by joints that divide it into prisms. It appears to bifurcate eastward, one 
portion running with a tolerably uniform thickness of a few feet as a prominent band at 
the top of the shales and sandstones, the other slanting upwards and gradually thinning 
away in the granophyre. 

Towards its base, near the contact with the underlying shales, the rock as usual 
becomes finer grained, and the thin band just referred to resembles in texture one of the 
wider basalt-dykes. Westwards the rock can be followed round the top of the grassy 
slopes formed by the decay of the shales. Though concealed by intervals of moorland 
and peat, it is visible in the stream sections, and I think must be continuous, as a band 
only a few yards thick, round the northern side of the hills as far as Beinn Bhuidhe, 
where a similar sill makes a prominent crag. Its total area measures a mile and a quarter 
in length by half a mile in breadth. The granophyre which overlies it forms part of an 
interesting series of sheets which I have traced all the way from Suisnish to the braes 
above Skulamus. 

Whether or not the whole sheet of basic rock is continuous, and whether it all 
proceeded from the great Suisnish dyke, cannot be confidently decided, though from the 
great thickness of the sill at the dyke, its attenuation outwards from that centre and its 
uniformity of petrographical character, I am disposed to answer affirmatively. There is 
no other probable vent to be seen in the neighbourhood, unless a massive dyke that runs 
from Loch Fada north-westwards into Glen Boreraig can be so regarded. 

VOL. XXXV. PART 2. O 



118 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

Another example of the thicker type of sills may be selected from the promontory 
of Ardnamurchan.* The general form and position of this mass will be understood from 
the small map in Plate I. Forming the rugged shore for three quarters of a mile, it slopes 
thence inland in a series of rocky knolls, which in rather less than a mile culminate in the 
summit of Ben Hiant, 1729 feet above sea-level. The rock which covers this large space 
is disposed in numerous rude beds, which have a seaward dip of perhaps 15° to 20°. They 
are distinctly prismatic, and the prisms are not infrequently grouped in fan-shape. They 
are evidently due to different eruptions, but I observed no trace of any other rock 
intercalated between them. They are never, so far as I could discover, amygdaloidal 
nor do they present the ordinary external characters of the beds of the plateaux. They 
distinctly overlie the bedded basalts on their eastern and southern margins ; but west- 
wards they appear to lie transgressively across the edges of these rocks, and to the north- 
west they rest on quartzites and schists. An outlier from the main mass forms the pro- 
minent hill of Srbn Mhbr, and can be seen distinctly overlying the bedded basalts as well 
as the neck of agglomerate already described (fig. 30). The rock of Ben Hiant is for the 
most part a well crystallised, ophitic olivine-dolerite. A specimen taken from the shore 
on the west side of the mass was found by Dr Hatch to present under the microscope 
its augite in large plates, which enclose narrow laths and needles of plagioclase felspar as 
well as grains of olivine. All the felspars are in lath-shapes, sometimes extremely long and 
narrow. The iron-ore likewise assumes an ophitic character, enclosing rectangular portions 
of felspar. Another specimen, taken from the south-east side of the hill, showed under 
the microscope " a curious intermixture of two different structures. Scattered portions 
which show the usual ophitic structure, their felspar and augite occurring in large 
crystals, are, so to speak, imbedded in a ground mass which presents rather a basaltic type, 
its felspar, augite, and magnetite, in long thin needles, microlites, and other skeleton 
forms, being enclosed in a dark devitrified base." A third specimen, selected from one 
of the columnar sheets near the top of Ben Hiant, is " a fine grained dolerite (or gabbro) 
showing little ophitic structure, the augite occurring in roundish grains, and only slightly 
intergrown with the felspars, which are more or less lath-shaped. The rock contains a 
considerable quantity of black iron-ore in irregular grains and some dirty-green viridite." 
Still another variety of structure occurs in a specimen which I broke from one of the 
shore crags on the S.W. side of the hill. Under the microscope, it presents a beautiful 
aggregate of " skeleton crystals and microlites of plagioclase, with here and there a 
rectangular crystal, long slender microlites of augite, and short serrated microlites of 
magnetite, the whole being confusedly imbedded in a dark glassy base powdered over 
with a fine magnetite dust." 

In rambling over this Ardnamurchan rock 1 was often reminded of the great intrusive 
mass of Fair Head. One of the features in which the rocks of the two localities resemble 
each other is their tendency to assume a coarsely crystalline texture. In some parts of 

* This locality has been described by Professor Jddd, who believed the dolerites to be streams proceeding from a 
volcanic vent (Quart. Jour. Geol. Soc, xxx. (1874) p. 2G1). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 119 

Ben Hiant the individual crystals reach an inch or more in length. These more largely 
crystalline portions, however, do not form distinct bands so much as patches in the midst 
of the general mass ; at least I did not notice any examples of such veins of segregation 
as are so prominent in Antrim. 

Owing to the denudation, which has laid this mass bare, no trace now remains of the 
rocks which covered it. That it is really an intrusive mass and not a superficial outflow, 
as Professor Judd supposed, may be inferred from the way it slants across the 
beds of the plateau, and also from its petrographical characters, in which it agrees 
with other undoubtedly intrusive rocks of the same series. None of the rocks which 
unquestionably flowed out on the surface present this coarsely crystalline structure. On 
the south-east of Ben Hiant, I observed at two places where the bedded basalts could be 
traced close up to the intrusive mass that the former presented the same dull indurated 
character which I have referred to as occurring near intrusive bosses on the plateaux. 
As shown on the small map in Plate I., two marked dykes diverge from the main mass 
of dolerite and run for some distance north-eastward. One of these, fully a mile long, 
descends into the valley and rises up into the basalt-plateau on the further side. 
Possibly these may be two of the feeders from which the thick mass of Ben Hiant was 
supplied. 

But infinitely more frequent in the west of Scotland is the second type of intrusive 
sheet, where, instead of lying in lenticular, coarsely-crystalline sills, the eruptive rock 
occurs in thin sheets, interposed with sometimes most deceptive regularity between the 
bedding planes of the rock which it traverses. It is this type which has become so familiar, 
from the descriptions and sections of Maccdlloch, as characteristically given in his 
account of Skye and in his drawings of the east coast of Trotternish in plate xvii. of 
his illustrations already cited. The height to which the base of the basalt escarpment 
rises on that side of the island, and the fine range of cliffs which there underlie it, permit 
the phenomena of intrusive sheets to be studied better than perhaps anywhere else in 
Britain. The erupted material has been thrust between the stratification planes of the 
Jurassic strata, between the strata and the overlying bedded basalts, and between the 
individual sheets of basalt. As Macculloch well shows, many sheets of intrusive rock, 
if seen only at one point, might readily be supposed to be regularly interstratified ; but 
perhaps only a few yards distant they may be found to break across the bedding, and to 
resume their course on a different level. 

The phenomena of the eastern coast of Trotternish are repeated on the east side of 
Eaasay, in Eigg, and in Mull. As a single example of them, I may select the accompany- 
ing section (fig. 35) from the east side of Eigg. Over the Jurassic sandstones (aa) a 
sheet of basalt (1) four to six feet thick has been injected between the stratification of 
the sandstones, and another (2) two to four feet thick has forced its way across the 
middle of one of the bedded basalts (bb) in which it bifurcates, and above which comes the 
thick series of lavas of the plateau (c, d). In one of the streamlets, which exposes a 
section of the Jurassic strata below the volcanic escarpment, more than twenty intrusive 



120 



DR' GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



> 

t 



wsxm 



I'M 



L> 



III 



iA-i 




sheets may be counted among the shales and limestones. They are sometimes not six 

inches thick, and seldom exceed six or eight feet. # 

It is observable generally throughout the west of Scotland, that the rock of the sills 

is more coarsely crystalline than that of the dykes, which in turn is generally not so fine- 
grained as that of the bedded basalts, but that the 
development of the crystalline structure is usually 
proportionate to the thickness of the mass. On the 
whole, the thinnest sheets are finest, and the thickest 
are coarsest in grain. But as they never reach the 
dimensions of the Antrim mass, they do not present 
such a largely crystalline texture as can be seen at 
Fair Head. It is further noticeable that, while they 
tend to lie between the bedding planes of the rocks 
which they traverse, they frequently break across 
them. What is most singular in this respect is their 
occasional disruption of one of the solid columnar 
or amorphous basalts, as in the example from Eigg 

^\ just cited, where one might have supposed that the 

ig. »— ec ion o siow e e an path of least resistance would have been much more 

Intrusive Sheets, Eigg. r 

readily found along the line of junction between two 
beds. Again, the abundance of intrusive sheets about the base of the volcanic plateaux 
contrasts strongly with their scarcity or absence higher up. We may examine miles of 
the central and higher parts of the basalt-escarpment without detecting a single example 
of them, but if the escarpment is cut down to the base we seldom need to search far to 
find them in numbers. 

If we consider the facts which have now been adduced regarding the position and 
structure of the Intrusive Sheets, we are led, I think, to regard these masses as belonging 
to the history of the basalt-plateaux, but to a comparatively late part of it. They 
consist of essentially the same materials as the lavas that form these plateaux, though 
with the difTerences of structure that the conditions of their production would lead us 
naturally to expect. Where they occur in thick masses, they have obviously been able to 
cool much more slowly at some depth beneath the surface than the comparatively thin 
beds could do that were poured out above ground, and hence they have there assumed a 
far more largely crystalline texture than was possible for them under other conditions. 
Their extraordinary number about the base of the basalt-escarpment points, in my 
opinion, to the increasing difficulty which the gradual thickening of the basalt-series 
presented to the uprise of molten matter. That the plateaux were rent open and that 
lava rose in the fissures thus caused, even after a depth of 2000 or 3000 feet of basalt had 
been piled up, is proved by the height to which dykes can be traced in Mull and else- 
where. But there would no doubt come a time when the vents would grow fewer, and 

* Quart. Jour. Geol. Soc, xxvii. (1871) p. 297. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 121 

when the pent-up volcanic energy would be unable to open new ones. Through the 
shattered crust the lava would be forced upwards, but the deep overlying cover of 
bedded basalts would present a formidable obstacle to its further ascent. Unable to find 
ample enough egress through such fissures as might be formed in the pile of basalts, the 
molten rock would seek its lines of least resistance along the planes of the strata and the 
lower basalt-beds; and there, accordingly, we find the sills in extraordinary profusion. 
They are no doubt of all ages in the progress of the building up of the volcanic plateaux, 
but I am disposed to believe that a large number of them may belong to the very latest 
period of the uprise of basalt within the area of Britain. 

In closing this history of the accumulation of the great Tertiary volcanic plateaux of 
this country, I would remark that as the result of prolonged eruptions from innumerable 
vents, the depression that stretched from the south of Antrim to the Minch was gradually 
in large measure filled up. We know that the pile of basalt-sheets reached in some places 
a depth of more than 3000 feet, and that not improbably it stretched in one continuous 
field of black lava along the west of Scotland and across the north of Ireland. That the 
lava spread round the base of the Highland mountains and ran up the Highland glens, 
much as the sea now does, is made clear from the position of the outliers of it which 
have been left perched on the ridges of Morven and Ardnamurchan. So far as can now 
be surmised, these wide Phlegrsean fields were only varied by a few volcanic cones 
scattered over their surface, marking some of the last vents from which streams of basalt 
had flowed. But the volcanic energy was still far from exhaustion. After the accumu- 
lation of such a deep and far extended sea of lava, those underground movements which 
produced the fissures that served as channels for the uprise of the dykes through all the 
older rocks continued to show their vigour. The covering of bedded lavas, though 
several thousand feet thick, was rent open by innumerable long parallel fissures in the 
prevalent north-westerly direction, up which basic lavas rose to form dykes. Whether 
the outflow of the bedded basalts had wholly ceased when the last dykes were injected 
into the plateaux cannot be told. Nor is there any evidence whether it had ended before 
the next great episode of the volcanic history — the extravasation of the gabbro bosses. 
All that we can affirm with certainty is, that the formation of north-west fissures and the 
uprise of basalt in them were repeated, for we find N.W. basalts traversing even the 
crests of the later eruptive masses of basic and acid rocks. It is difficult to suppose that 
none of these latest dykes communicated with the surface, and gave rise to cones with 
the outpouring of basalt and the ejection of dust and stones. But of such later 
manifestations of volcanic activity on the surface of the plateaux no undoubted trace can 
now be recognised. 



122 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



III. THE BOSSES AND SHEETS OF GABBRO. 

In singular contrast to the nearly flat basalts of the plateaux, another series of rocks 
rises high and abruptly above these tablelands into groups of dome-shaped, conical, spiry, 
and rugged hills. It is these heights which more than any other feature relieve the 
monotony of the wide areas of almost horizontal stratification so characteristic of the 
volcanic region of the north-west. Their geological structure and history are much less 
obvious than those of the bedded basalts. Their mountainous forms at once suggest a 
wholly different origin. Some portions of them have even been compared with the 
oldest or Archaean rocks.* That they are really portions of the Tertiary volcanic series, 
and that they reveal a wholly distinct phase in the history of volcanic action, is now 
frankly admitted. Whether we regard them from the petrographical or structural point 
of view, they naturally arrange themselves into two well-defined groups. Of these one 
consists of highly basic compounds, of which olivine-gabbro is the most prominent. The 
other comprises numerous varieties — granite, granophyre, felsite, quartz-porphyry, 
trachyte, pitchstone, and others — all of them being decidedly acid, and some of them 
markedly so. For reasons which will appear in the sequel, the former group must be 
considered as the older of the two, and it will therefore be described first. 

§ 1. Petrography. 

Since the publications of Macculloch, the occurrence of beautiful varieties of highly 
basic rocks among the igneous masses of the Western Isles has been familiar to geologists. 
They were named by him "hypersthene rock" and "augite rock," t names which 
continued in use until 1871, when my friend Professor Zirkel published the results of 
his tour through the west of Scotland, and showed that the rocks in question were 
mostly true gabbros. | Since his observations were published some of these rocks have 
formed the subject of important papers by Professor Judd. § 

The general petrographical characters of the gabbro areas of western Scotland may be 
summarised as follows : — A very considerable variety of petrological structure and 
chemical composition is observable among the rocks. At the one end of the series are 
compounds of plagioclase and augite, which, though wanting in olivine, have the general 
structure and habit of dolerites. At the other end are mixtures wherein felspar is scarce or 
absent, and where olivine becomes the chief constituent. Between these two extremes are 
many intermediate grades, of which the most important are those containing the variety of 
augite known as diallage and also olivine. These are the olivine-gabbros, which form so 

* This was my own first impression, when I began, as a boy, to ramble among them. Macculloch had correctly 
grouped them with the other overlying rocks, and this conclusion was afterwards confirmed by Zirkel. 
t Western Islands of Scotland, vol. i. pp. 385, 484. 
X Zeitschrift. Deutsch. Geol. Gesellsch., xxiii. (1871) p. 1. 
§ Quart. Jour. Geol. Soc, xli. (1885) p. 354, xbi. (1886) p. 49. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 123 

marked a feature in the central parts of the great basic bosses. That some of these 
varieties of rock pass into each other cannot be doubted. Their distinctive composition 
and structure appear to have been largely determined by their position in the eruptive 
mass. The outer and thinner sheets are in great measure dolerites, with little or no 
olivine. The coarse gabbros are found in the inner portions. Eocks rich in olivine, 
however, occur at the outer and especially the lower part of the gabbro boss of Eum. 
The following leading varieties may be enumerated. 

Dolerite. — This rock varies from an exceedingly close grain (when it approaches and 
graduates into basalt) up to a coarse granular crystalline texture, in which the component 
minerals are distinctly visible to the naked eye. An average sample is found to consist 
of plagioclase, usually lath-shaped, and crystals or grains of augite with or without 
olivine. Under the microscope, the different varieties are distinguished by the presence 
of more or less distinct ophitic structure, the felspar being enveloped in the augite. 
For the most part they are noncrystalline, but occasionally show traces of a glassy base. 
Ilmenite is not infrequent, with its characteristic turbid decomposition product 
(leucoxene). In other cases the iron-ore is probably magnetite. Between the dolerites 
and gabbros no line of demarcation can be drawn in the field, nor can a much more 
satisfactory limitation be made even with the aid of the microscope. As a rule, the 
thickest and largest intrusive masses or bosses are gabbro, those of less size are 
dolerite, while the smallest (and sometimes the edges of the others) assume the aspect of 
basalts. 

Gabbro. — Under this term I arrange, as proposed by Professor Judd, all the coarse- 
grained granitoid basic rocks of the region without reference to the variety of augite 
present in them. Under the microscope, they are found to be holocrystalline, but with 
a granitic rather than an ophitic structure, though traces of the latter are by no means 
rare. To the naked eye their component minerals are usually recognisable. Professor 
Zirkel, from his examination of the Mull gabbros, believed them to consist of three 
parts of plagioclase, two parts of olivine, and one part of diallage.* Olivine, however, is 
not invariably present. t The pyroxene also does not always show the peculiar fibrous 
structure of diallage. Professor Judd, indeed, maintains that the diallagic form is due to 
a deep-seated process of alteration (schillerization), and that the same crystal may consist 
partly of ordinary augite and partly of diallage.J Ilmenite (with leucoxene), magnetite, 
apatite, biotite, and epidote are not infrequent constituents. 

Troctolite (Forellenstein). — This beautiful variety of plagioclase-olivine rock occurs as 
a conspicuous feature on the east side of the gabbro-boss of the island of Eum. It forms 
a bed on the side of the mountain Allival, in which the component minerals are drawn 

* Zeitschr. Deutsch. Geol. Gesellsch., xxiii. (1871), p. 59. 

t Professor Judd (Quart. Jour. Geol. Soc, xlii p. 62) believes that originally all the gabbros contained olivine, 
and that where it is now absent, it has been altered into magnetite or serpentine. 

% Op. cit., xli. In a later paper he insists on the gradation of the coarse granitoid varieties (gabbros) into 
holocrystalline compounds, where the felspar appears in lath-shapes with crystals or rounded grains of augite and 
olivine (dolerites), and thence into true basalts, magma-basalts, and tachylytes (op. cit, xlii. p. 62). 



124 DR GEIK1E ON THE HISTORY OF VOLCANIC ACTION 

out parallel with the upper and under surfaces of the bed. So marked is this flow- 
structure that hand-specimens might readily be taken at the first glance for ancient 
schistose limestone. " The felspathic ingredient (probably labradorite or anorthite) is 
white, and its lath-shaped crystals have ranged themselves with their long axes parallel 
to the line of flow. The olivine occurs in perfectly fresh grains, which in hand-specimens 
have a delicate green tint. Under the microscope they appear colourless, and are pene- 
trated by the felspar prisms in ophitic intergrowth. There is a small quantity of a pale 
brownish augite, which not only occurs in wedge-shaped portions between the felspars, 
but also as a narrow zone round the olivines." # Considerable differences are visible in 
the development of the flow-structure, and with these there appear to be accompanying 
variations in the microscopic structure. Dr Hatch to whom I submitted my specimens, 
informs me that in one of them, where the flow-structure is so marked as to give a finely 
schistose aspect to the rock, " there is a larger proportion of augite, some of which exhibits 
a distinct diallagic striping ; the olivine grains show no ophitic structure, but are some- 
times completely imbedded in the augite." To this remarkable flow-structure I shall 
again refer in connection with the light it throws on the bedded character of the exterior 
of the gabbro bosses. 

Between these different basic igneous rocks of the Inner Hebrides, as Professor Judd 
has shown, there are many gradations according to the varying proportions of the chief 
component minerals. Thus from the olivine-gabbros, by the diminution or disappearance 
of the augite we get such rocks as troctolite ; where the plagioclase diminishes or 
vanishes, we have the different forms of picrite ; where the olivine is left out, we come to 
compounds, like eucrite ; while by the lessening or disappearance of the felspar and augite, 
we are led to ultra basic compounds, consisting in greatest part of olivine like lherzolite 
and dunite. 

§ 2. Relations to the other Volcanic Rocks. 

Various opinions have been expressed regarding the connection between the 
amorphous eruptive rocks of the hill-groups and the level basalt-sheets of the 
plateaux. Jameson, though he landed at Rudh' an Dunain, in Skye, where this 
connection can readily be found, does not seem to have made any attempt to 
ascertain it. He noticed that the lower grounds were formed of basalt, and that 
the mountains "appeared to be wholly composed of syenite and hornblende rock, 
traversed by basalt veins." t Macculloch, in many passages of his Western Islands, 
alludes to the subject as one which he knew would interest geologists, but about 
which he felt that he could give no satisfactory information, and with characteristic 
verbiage he refers to the impossibility of determining boundaries, to the transition 
from one rock into another, to the inaccessible nature of the ground, to the almost 
insuperable obstacles that impede examination, to the distance from human habita- 

* MS. of Dr Hatch. 

t Mineraloyical Travels (1813), vol. ii. p. 72. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 125 

tion, and to the stormy climate, — a formidable list of barriers, in presence of which 
he leaves the relative position and age of the rocks unsettled.* 

Von Oyenhausen and Von Dechen, who wrote so excellent an account of their visit 
to Skye, and who traced much of the boundary-line between the gabbros and the other 
massive eruptive rocks (syenite), seem to have made no attempt to work out the 
connection between the former and the rest of the volcanic rocks, t 

Principal Forbes, in his able sketch of the Topography and Geology of the 
Cuchullin Hills, appears to have been the first to recognise the superposition of the 
" hypersthene rock " upon the "common trap rocks " — that is, the plateau-basalts. He 
was disposed to consider the " hypersthene mass as a vast bed, thinning out both ways, 
and inclined at a moderate angle towards the S.E."| 

Professor Judd regarded the bosses of basic and acid rocks that rise out of the bedded 
basalts as the basal cores of enormously denuded volcanic cones. He believed the 
granitoid rocks to have been first erupted, and that after a long interval the basic masses 
were forced through them, partly consolidating underneath and partly appearing at the 
surface as the plateau-basalts. § That the order of appearance of the several rocks 
has been exactly the reverse of this supposed sequence will, I think, be fully established 
in the present memoir. Professor Zirkel recognised that the gabbros are a dependence 
of the basalts, that they overlie them, and that on the naked flanks of the mountains 
they are regularly bedded with them. || 

So far as I can learn, however, no one has yet traced out in more detail the actual 
boundaries of the several rocks on the ground, so as to obtain evidence of their true 
relations to each other as regards structure and age. Some of the numerous impedi- 
ments recorded by Macculloch have no doubt retarded the investigation. But, as 
Forbes so well pointed out, there is really no serious difficulty in determining the true 
structural connection of the amorphous rocks with each other and with the bedded 
basalts of the plateaux. I have ascertained them in each of the districts,! and as the 
result of my examination I may briefly state here that there cannot be the least doubt 

* See his Western Islands, vol. i. pp. 368, 374, 385, 386. With much admiration for the insight and zeal, amount- 
ing almost to genius, which Macculloch displayed in his work among the Western Islands, at a time when, with poor 
maps and inadequate means of locomotion, geological surveying was a more difficult task than it is now, I have found it 
impossible to follow in his footsteps with his descriptions in hand, and not to wish that for his own fame he had been 
content to claim credit only for what he had seen. His actual achievements were enough to make the reputation of 
half-a-dozen good geologists. It was unfortunate that he did not realise how inexhaustible nature is, how impossible 
it is for one man to see and understand every fact even in the little corner of nature which he may claim to have 
explored. He seems to have had a morbid fear lest any one should afterwards discover something he had missed; he 
writes as if with the object of dissuading men from travelling over his ground, and he indeed tacitly lays claim to any 
thing they may ascertain by averring that those who may follow him " will find a great deal that is not here described, 
although little that has not been examined " (p. 373). Principal Forbes long ago exposed this weak side of Maccul- 
loch and his work {Edin. New Phil. Jour., xl. (1846) p. 82). 

t Karsten's Archiv, i. p. 99. They frankly admit that " the relation of the hypersthene-rock to the other trap 
rocks was not ascertained." j Edin. New Phil. Jour., xl. (1846) pp. 85, 86. 

§ Quart. Jour. Geol. Soc, xxx. (1874) p. 249. || Zeitschrift. Deutsch. Geol. Gesellsck, xxiii. (1871) pp. 58, 92. 

II In two of my excursions in Mull, and once in Skye, I was accompanied by my colleague Mr H. M. Cadell, and 
I gladly acknowledge the great assistance he rendered me in mapping those regions. 

VOL. XXXV. PART 2. v 



126 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

that the amorphous bosses, both basic and acid, are younger than the surrounding bedded 
basalts, and that the acid protrusions are on the whole younger than the basic. I shall 
now proceed to show how these conclusions are established by the evidence of each of 
the areas where the several kinds of rock occur. 

(a) Skye. — By far the largest, most picturesque, and to the geologist most im- 
portant area of gabbro in Britain, is that of Skye. Though like every other portion of 
the volcanic region, it has suffered enormous denudation, and has thereby been trenched 
to the very core, it reveals, far more conspicuously and clearly than can be seen anywhere 
else, the relation of the gabbro to the bedded basalts on the one hand, and to the acid 
protrusions on the other. Its chief portion is that which rises into the group of the 
Cuillin Hills, which for blackness of hue, ruggedness of surface, jaggedness of crest, and 
general grimness of aspect, have certainly no rivals within the limits of the British Isles. 
It has long been known to extend eastwards into Blath Bheinn (Blaven) and its immediate 
northern neighbours. There is, indeed, no break whatever between the rock of the 
Cuillins and that of the hills on the east side of Strath na Creitheach. In Strath More 
the gabbro is interrupted by the granitoid mass of the Red Hills. Patches of it, however, 
occur further to the east, even as far as the Sound of Scalpa. If we throw out of 
account the invading granitoid rocks, and look upon the whole tract within which the 
gabbro occurs as originally one connected area, we find that it covered an elliptical space 
measuring about nine miles from S.W. to N.E. and six miles from N.W. to S.E., and 
embracing at least forty square miles.* But that its original size was greater is strikingly 
shown more particularly on the western margin, which like that of the basalt-escarpments, 
has obviously been determined by denudation, for its separate beds present their trun- 
cated ends to the horizon all along the flanks of the Cuillins, from the head of Glen 
Brittle round to Loch Scavaig (fig. 36). 

The first point to be ascertained in regard to the gabbro and its associated basic rocks 
of the mountainous tract is their connection in geological structure and age with the 
bedded basalts of the plateau. This initial and fundamental relation, as Forbes long ago 
said, can be examined along the whole western and southern flank of the Cuillin Hills, 
from the foot of Glen Sligachan round to the mouth of Loch Scavaig. Even from a 
distance, the observer, who is favoured with clear weather, can readily trace the almost 
level sheets of basalt till they dip gently under the darker rock of the hills. Tourists, 
who approach Skye by way of Loch Coruisk, have an opportunity, as the steamer nears 
the island of Soay, of following with the eye the basalt-terraces of the promontory of 
Rudh' an Dunain until they disappear under the gabbro of the last spur of the Cuillins 
that guards the western entrance to Loch Scavaig. 

What is so evident at a distance becomes still more striking when viewed from nearer 
ground. Nowhere can it be more impressively seen than at the head of Glen Brittle. 
Looking westwards, the traveller sees in front of him only the familiar level terraces and 

* Though this and the other bosses are here spoken of as consisting of gabbro, it will be understood that this rock 
only constitutes the larger portion of their mass, which includes also dolerites, basalts, and other basic compounds. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 127 

green slopes of the basalt-plateau, rising platform above platform to a height of -nearly 
1500 feet above the sea. But turning to the east, he beholds the dark, gloomy, cauldron- 
like Corry na Creiche, from which rise some of the ruggedest and loftiest crests of the 
Cuillins. On the hills that project from either side of this recess and half inclose it, 
the bedded basalts mount from the bottom of the valley, with their lines of parallel terrace 
dipping gently inward below the black rugged gabbro that crowns them and sweeps 
round to form the back or head of the corry. Down the whole length of Glen Brittle 
the same structure conspicuously governs the topographical features. On the right hand, 
the ordinary terraced basalts form the slopes ; and they rise for some 500 or 600 feet up 
the eastern side, until they pass under the darker, more rugged, and less distinctly bedded 
rocks of the mountains (fig. 36). The dip of the whole series is here at a gentle angle 
toward S.E. , or into the main mass of the Cuillin group. 

When, however, we proceed to examine the junction between the two rocks we find 
it to be less simple than it appears. It is not an instance of mere superposition. The 
gabbro unquestionably overlies the basalts, and is therefore of younger date. But it 
overlies them, not as they rest on each other, in regular conformable sequence of eruption, 
but intrusively, as a sill does upon the rocks on which it appears to follow in the unbroken 




Fig. 36. — Section across Glen Brittle, to show the general relations of the Bedded Basalts (a) and the Gabbros (6). 

order of accumulation. This important structure may be ascertained in almost any of 
the many sections cut by the torrents which have so deeply trenched with gullies the 
flanks of the hills. Starting from the ordinary bedded basalts, we observe in mounting 
the slopes and approaching the gabbro that the rocks insensibly assume that indurated 
sbattery character, which has been referred to as characteristic of them round the 
margins of vents. Beds of dolerite make their appearance among them, which are so 
distinctly crystalline, and so resemble in character the rocks of the sills, that there can be 
little hesitation in regarding them as intrusive. These sills increase in size and number 
as we ascend, though hardened amygdaloidal basalts may still be observed. True gabbros 
then supervene in massive beds, and at last we find ourselves entirely within the gabbro 
area, where, however, thin bands of highly altered basalt still for some distance appear. 
One further fact will generally be noticed, viz., that before reaching the main mass of 
gabbro, veins and sills of basalt, as well as of various felsitic and porphyritic members of 
the acid group, come in abundantly crossing and re- crossing each other in the most intri- 
cate network. The base of the thick gabbro-sheets is thus another horizon on which, 
like that below the plateau-basalts, intrusive masses have been especially developed. 



128 DRGEIKIE ON THE HISTORY OF VOLCANIC ACTION 

Through all these rocks numerous parallel basalt-dykes, running in a general persistent 
N.N.W. direction, rise from below the sea-level up even to the very crests of the Cuillins. 

The sections on the westerD side of the area thus prove that the gabbro inosculates 
with the bedded basalts by sending into them, between their bedding planes, sheets 
which vary in texture from fine dolerites at the outside into coarse gabbros further 
towards the central mass, and that this intrusion has been accompanied by a certain 
amount of induration of the older rocks. 

On the eastern side, the same structure can be even more distinctly seen, for it is 
not only exposed in gullies and steep declivities, but can be traced outward into the basalt- 
plateau. In the promontory of Strathaird, Jurassic sandstones and shales, which form 
almost the whole of the coast-line and lower grounds, are surmounted by the bedded 
basalts. Denudation has cut the plateau into two parts. The smaller of these makes the 
outlier that rises into Ben Meabost (1128 feet). The larger stretches continuously from 
Glen Scaladal and Strathaird House northward into Blath Bheinn. Hence from the 
ordinary terraced basalts, with their amygdaloids. thin tuffs, red partings, and seams of 
lignite, every step can be followed into the huge gabbro mountain. Starting from the 
black shales on which the lowest basalt lies, we walk over the successive terraces up into 
the projecting ridge of An da Bheinn. But as we ascend, sheets of dolerite and gabbro 
make their appearance between the basalts, which gradually assume the altered aspect 
already noticed. The dip of the whole series is at a low angle northwards, and the beds 
can be followed round the head of the Glen nac Leac into the southern slopes of Blath 
Bheinn. Seen from the eastern side of this valley, the bedded character of that mountain 
is remarkably distinct, but it becomes less marked towards the upper part of the ridge 
where the gabbros preponderate. One of the most striking features of the locality is the 
number and persistence of the N.W. dykes, which strike across from the ordinary 
unaltered basalts of the plateau up into the highest gabbros of the range. Less durable 
than the intractable gabbro, they have weathered out where they run up its precipices, 
thereby causing the vertical rifts and gashes and the deep notches on the crest that 
form so marked a feature in the scenery. On the other hand, they are often less 
destructible than the plateau-basalts, and hence in the Glen nac Leac they may be seen 
projecting as low dams across the stream which throws itself over them in picturesque 
waterfalls. 

The deep dark hollow of the Coire Uaigneich has been cut out of the very core of 
Blath Bheinn, and lays bare the structure of the east part of the mountain in the most 
impressive as well as instructive way (Fig. 37). By ascending into this recess from Loch 
Slapin, we pass over the whole series of rocks, and can examine them in an almost con- 
tinuous section in the bed of the stream and on the bare rocky slopes on either side. 
Sandstones and shales of the Jurassic series extend up the Allt na Dunaiche for nearly a 
mile, much veined with basalt and quartz-porphyry, by which the sandstones are locally 
indurated into quartzite. At last these strata are overlapped by the basalts of the Strath- 
aird plateau, which with a marked inclination to N.N.W., here dip towards the mountains. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 129 

But by the time these rocks have reached this valley, they have already lost, their 
usual brown colour and crumbling surfaces, and have assumed the indurated splintery 
character, though still showing their amygdaloidal structure. They are much traversed 
by veins and strings of felsite and quartz-porphyry, which rocks at last appear as a broad 
band that runs up the bottom of the Coire Uaigneich, and ascending the col, crosses it 
south-westwards into the Glen nan Leac. On the left or south-eastern side of this intrusive 
mass, a portion of Lower Silurian quartzite and limestone (here and there altered into 
white marble) is traceable for several hundred yards up the stream.* Whether this is 
really in place, and projects as the top of an eminence round and over which the volcanic 
rocks were accumulated, or whether it is a mass that has been torn away and carried 
upward during some of the paroxysms of eruption, I could not determine. Knowing 
how large are the portions of schist embedded between the basalts of Mull, I do not 
think the great size of this mass necessarily precludes us from regarding it as displaced 
in the same way. "Where the quartzite and limestone first appear at the lower part of 
the valley, they present an interesting example of that sheared structure with which 
recent investigations in the North- West Highlands have now made us familiar.t The 
two rocks have been ground into each other so as to produce a compound that is neither 
limestone nor quartzite, but a calcareous quartzose schist, in which the beautifully parallel 
planes of division that mark the surfaces of movement bear the closest resemblance to flow- 
structure. There can be no doubt that here in the midst of the Tertiary volcanic masses, 
and not improbably as a result of volcanic explosion, there is revealed to us the existence 
underneath this district of one of those great thrust-planes in the Silurian rocks which 
have had so powerful an influence in the production of the younger schists of the 
Highlands. The evidences of metamorphism and the formation of schists by mechanical 
movement after the Lower Silurian period, so abundant in the north of Sutherland, 
are thus found to continue southward even across the island of Skye. 

The bedded basalts of Strathaird, after dipping down towards the N.N.W., bend up 
where they are interbanded with dolerites and gabbros, and form the prominence called 
An Stac, which rises as the eastern boundary of the Coire Uaigneich. Their steep dip 
away from the mountain is well seen from the east side, and their outward inclination is 
continued into the ridge to the southward. Similar rocks appear on the other flank of 
the band of quartz-porphyry, and form the base of Blath Bheinn. The bedded basalts are 
everywhere of the usual altered, indurated, and splintery character. The intrusive sheets 
interposed between them become thicker and more abundant higher up, until they con- 
stitute the main mass of the hill. But that they are in separate sheets, and not in one 
amorphous mass, can be recognised by the parallel lines that mark their boundaries. 

The quartz-porphyry sends out veins into the surrounding rocks, and is obviously the 
youngest protrusion of the locality, except of course the N.N.W. basalt-dykes which 

* This limestone was noticed by Von Oeynhausen and Von Dechen, but they believed it to be a portion of the 
Lias torn off and carried upward by the eruptive rocks (Karsten's Archiv, i. p. 79). 

t This rock was first recognised by Mr H. M. Cadell, who accompanied me in one of my excursions over the ground. 



130 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



cross it, and which are nowhere seen in a more imposing display than round the flanks of 
Blath Bheinn. A section across the corry shows the structure represented in fig. 37. 

It is thus demonstrable that when its line of junction with the surrounding plateau- 
basalta is traced in some detail, the gabbro is found to overlie them as a whole, but also 
to be intercalated with them in innumerable beds, bands, or veins which rapidly die out as 
they recede outwards from the main central mass; that these interposed beds are intrusive 
sheets or sills proceeding from that mass, and that the contiguous bedded basalts show 
more or less marked metamorphism. We have now to consider the structure of the 
interior of the gabbro area of the Cuillin Hills. The first impression of the geologist who 
visits that wild district is that the main mass of rock is as thoroughly amorphous as a 
core of granite. Yet a little further examination will reveal to him many varieties of 
texture, sometimes graduating into, sometimes sharply marked off from, each other, and 
suggesting that the rock is not the product of one single protrusion. He will recognise 
further indications of successive discharges or extravasations of crystalline material 
during probably a protracted period of time, and in the intricate network of veins 
crossing each other and the general body of the rock in every direction, as well as in 




Fig. 37. --Section across the Coire Uaigneich, Skye. a, Silurian limestone and quartzite; b, Jurassic sandstones and shales; 
cc, bedded basalts and dolerites ; del, gabbros and dolerites with indurated basalts ; e, quartz-porphyry sending veins into 
surrounding rocks ; //, basalt-dykes running north-west through all the other rocks. 



the system of steady N.W. basalt-dykes that traverse all the other rocks, he will recognise 
the completion of the evidence of repeated renewals of subterranean energy. 

But he will be struck with the absence of the more usual proofs of volcanic activity 
in such forms as vesicular lavas and abundant masses of slag, bombs, and tuffs, which are 
commonly associated with the idea of the centre of a volcanic orifice. Everything around 
him suggests that he stands, as it were, far beneath that upper part of the earth's crust 
which is familiar to us in the phenomena of modern volcanoes ; that he has been admitted 
into the heart of one of the deeper layers, where he can study the operations that go on 
at the very roots of an active vent. He will notice that, on the whole, the rock is largest 
in grain towards the centre, some features of it around Loch Coruisk reminding him of 
the most coarsely-crystalline granites. Here and there too, he will observe details of 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



131 



structure that at once recall him to the internal arrangements of the thicker intrusive 
sheets, but they are displayed here on a still greater scale, as from the bulk of the huge 
boss of the Cuillin gabbro, might be expected. Portions of the rock show a remarkable 
segregation or flow-structure, the several minerals being arranged in parallel layers, 
which sometimes simulate the puckering of true schists. This structure is shown in 
fig. 38, the light bands consisting mainly of felspar, the darker of the ordinary gabbro, 
but here and there with the magnetite separated out into distinct lenticular folia. It is 
singular to find, in the midst of such coarsely crystalline material, exceedingly fine-grained 
masses of basalt, some of which are amygdaloidal. At the time when I made my last 
examination of this region, the six-inch Ordnance maps were not issued, and I found it 
impossible to trace out such details of geological structure on the uncontoured one-inch 
map, which was the only Ordnance sheet then available. I have every hope, however, 
that when the mapping of the Cuillin Hills is undertaken on the large scale maps, it 
will be possible to work out an exceedingly complex structure even in what might be 
thought to be thoroughly amorphous masses. 




Fig. 38. — Segregation-structure in the Gabbro, from the ridge between Meall Dearg and Loch Coruisk. 



There is one important feature which only a minute and patient survey can elucidate, 
Though I found among the Cuillins no distinct proof that the mass of gabbro ever gave rise 
to discharges of material, either lava-form or fragmentary, which reached the surface, I 
obtained unquestionable evidence of explosions and the production of pyroclastic masses. 
Among the moraine-mounds of Harta Corry, blocks of basalt-agglomerate are strewn 
about, full of angular fragments of altered basalt, sometimes highly amygdaloidal, and also 
boulders in which lumps of coarse gabbro are enveloped in a matrix of finer material. But 
I did not find the parent rocks from which these glacier-borne masses had been derived. 
That this huge boss of gabbro in Skye, besides invading and altering the bedded basalts, 
may have communicated eventually with the surface, and have given rise to superficial 
discharges, is not at all improbable, but of any such outflows not a vestige appears now 
to remain. We must remember, however, that the gabbro no doubt in many places 
found its readiest upward ascent in vents belonging to the plateau-period, and that 
portions of the agglomerates of these earlier vents may be expected to be found involved 
in it, like that of the great vent of the Red Hills. 

Before quitting this area, I will refer to the detached portions of gabbro inclosed in 
and lying to the east of the mass of the Red Hills. One of the best-marked of these forms 



132 DRGE1KIE ON THE HISTORY OF VOLCANIC ACTION 

a conspicous crag on the east side of Strath More, immediately to the north of Beinn na Cro. 
It consists of beds of coarse gabbro, with others of dolerite and basalt, and is traversed 
by veins from the granophyre of the glen, as well as by the usual N.W. basalt dykes 
(fig. 55). It appears to be a marginal portion of the main gabbro area separated by 
the intrusion of the great granitoid boss of the Red Hills. On the north-eastern side of 
Beinn na Caillich numerous intrusive sheets of gabbro and dolerite traverse the quartzite 
and limestone, and extend down to the sea-margin in the Sound of Scalpa. 

(b) Rum. — The mountains of the island of Rum, rising as they do from a wide 
expanse of open sea, present one of the most prominent and picturesque outlines in the 
West Highlands. Less accessible than most of the other parts of the volcanic region, 
they have been less visited by geologists. They were described by Macculloch as 
composed of varieties of " augite rock." He noticed in this rock "a tendency to the 
same obscurely bedded disposition as is observed in other rocks of the trap family," 
and found at one place that it assumed "a regularly bedded form, being disposed in 
thin horizontal strata, among which are interposed equally thin beds of a rock resembling 
basalt in its general characters."""" Professor Judd repeats Macculloch's observation, that 
" the great masses of gabbro in Rum often exhibit that pseudo-stratfication so often 
observed in igneous rocks." He regards these masses, like those of Skye and Mull, as 
representing the core of a volcano from which the superficial discharges have been 
entirely removed, and he gives a section of the island in which the gabbro is repre- 
sented as an amorphous boss sending veins into a surrounding mass of granite.t In a 
more recent paper he has given an excellent detailed account of the mineralogical 
composition of some of the remarkably varied and beautiful basic rocks constituting the 
hills of Rum, but adds no further information regarding the geological structure of the 
island.^ 

Even from a distance of eight or ten miles, the hills of Rum are seen to be obviously 
built up of successive nearly horizontal tiers of rock. As the summer tourist is carried 
past the island, in that wonderful moving panorama revealed to him by the " swift 
steamer " of modern days, these great dark cones remind him of colossal pyramids, and 
as the ever- varying lights and shadows reveal more prominently the alternate nearly 
level bars of crag and stripes of slope, the resemblance to architectural forms stamps 
these hills with an individuality which strikes his imagination and fixes itself in his 
memory. If choice or chance should give him a nearer view of the place, he would 
not fail to notice that it is among the northern hills of the island that the bedded 
character is so conspicuous, and that it ceases to be prominent in the southern 
heights. Crossing over from Eigg, he would recognise each of the features represented 
in the sketch reproduced in fig. 39. Along the shore, red (Torridon) sandstones 
rise in naked cliffs, from the top of which the ground seems to slope upward in 
brown moors to the bare rocky declivities. A deep valley (Glen Dibidil) is seen to 

* Western Islands, i. p. 486. t Quart. Jour. Geol. Soc, xxx. p. 253. 

X Op. cit., xli. (1885) p. 354. See also his paper in vol. xlii. of the same Journal. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



133 



run into the heart of the hills between the bedded group to the north and the 
structureless group to the south. If the weather is favourable, some eight or more 
prominent parallel bars of rock may be counted on the two higher cones to the right. 
These bars are not quite level, but appear to have a gentle inclination from right 
to left. They remind one of the terraced basalts of the plateaux, but present a 
massiveness and a breadth of intervening bare talus-slope such as are not usual among 
those rocks. 

Nor is this impression of regularity and bedded arrangement lessened when we 
actually climb the slopes of the hills. I had for years been familiar with the outlines of 
Eum as seen from a distance, and had sketched them from every side, but I shall never 
forget the surprise and pleasure when my first ascent of the cones revealed to me the 
meaning of these parallel tiers of rock. I found it to be the structure of the Cuillin 
Hills repeated, but with some minor differences which are of interest, inasmuch as they 
enlarge our conceptions of the process by which the gabbro-bosses were formed. 

The northern half of the island of Rum consists almost entirely of red sandstone, 
which is obviously a continuation of the same massive formation so well developed around 




Fig. 39. — Outline of the Hills of the Island of Rum, sketched from near the Isle of Eigg. 



Loch Torridon and traceable between the Archaean gneiss and the Lower Silurian strata 
up as far as Cape Wrath. The sandstones, though full of false bedding, show quite 
distinctly their true stratification, which is inclined with singular persistence towards 
W.N.W., at angles averaging from 15° to 20°. If they are not repeated by folds or faults, 
they must reach in this island a thickness of some 10,000 feet. Their red or rather 
pinkish tint seems mainly to arise from the pink felspar so abundant in them, for in 
many places they really consist of a kind of arkose. Pebbly bands with rounded pieces 
of quartz are of common occurrence throughout the whole formation. Dykes and veins 
of basalt are profusely abundant. Sometimes these run with the bedding, and might at 
a distance be taken for dark beds among the pink sandstones. They often also strike 
obliquely up the face of the cliffs like ribbons. 

But, notwithstanding their apparent continuity, there can be no doubt that these 
sandstones have suffered from those powerful terrestrial disturbances which have affected 
all the older rocks of the North- West Highlands. On the west side, where they plunge 
steeply into the sea, they have undergone a change into fine laminated rocks, which might 
at first be mistaken for shales, but which owe their fissility to shearing movements. 

VOL. XXXV. PART 2. S 



134 DR OEIKIE ON THE HISTORY OF VOLCANIC ACTION 

Along their southern border, from a point on the east coast near Bagh-na-h-Uamha, south 
of Loch Scresort, to the head of Kilmory Glen, they are abruptly truncated against a group 
of dark, flaggy, and fissile schists and fine quartzites or grits, which in some places are black 
and massive like basalt, and in others are associated with coarse grey gneiss. That some 
of these rocks are portions of the Archaean series can hardly be doubted, and the vertical 
separations and apparent transitions are probably repetitions of the faults and thrust- 
planes of the north-west. I found also on the northern slopes of Glen Dibidil a patch of 
much altered grey and white limestone or marble, which reminded me of the Lower 
Silurian limestone of Skye. 

In passing over the zone of these more ancient rocks, we find them to present 
increasing signs of alteration as they are traced up the slopes towards the great central 
mass of erupted material. The pink sandstones gradually lose their characteristic tint, 
and grow much harder and more compact, while the veins and dykes of basalt and 
sheets of dolerite intersecting them increase in number. The zone of black compact 
quartzite, which lies to the south of the sandstones, and which at one point reminds us of 
basalt, at another of the flinty slate of the schistose series, likewise displays increasing 
induration. Its bedding, not always to be detected, is often vertical and crumpled. 
But the most remarkable point in its structure is the intercalation in it of bands of 
breccia. These vary from less than an inch to several yards in diameter ; they run 
mostly with the bedding, but occasionally across it. The stones in them are fragments 
of the surrounding rock imbedded in a matrix of the same material, but also with pieces 
of a somewhat coarser grit or quartzite. A band of coarse breccia forms the southern 
limit of this zone along the northern base of Barkeval and Allival. In general character 
it resembles the thinner seams of the same material just referred to. The matrix so 
closely agrees with the black flinty quartzite, that but for the included stones it could 
hardly be distinguished; so greatly has the mass been indurated that the stones seems to 
shade off into the rest of the rock. But here and there its true brecciated nature is 
conspicuously revealed by prominent blocks of hardened sandstone. This band of breccia 
must in some places be 150 or 200 feet broad. It has no distinct bedding, but seems to 
lie as a highly inclined bed dipping into the hill. It is at once succeeded by a black 
flinty felsite like that of Mull. The ground-mass of this rock, so thickly powdered with 
magnetite grains as to be almost opaque under the microscope, displays good flow- 
structure round the turbid crystals of orthoclase and the clear granules of quartz. 
Further up the hill, the rock becomes lighter in colour and less flinty in texture — a 
change which is found to arise from more complete devitrification, the ground-mass 
having become a crystalline granular aggregate of quartz and felspar with scattered 
porphyritic crystals of these minerals (microgranite). In some places, the felsite incloses 
fragments of other rocks. A specimen of this kind, taken from the head of Coire Dubh, 
shows under the microscope a brown microfelsitic ground-mass, with crystals of felspar 
and augite, inclosing a piece of basalt, composed of fine laths of plagioclase, abundant 
magnetite, and a smaller proportion of granules of augite. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



135 



This band of felsite and microgranite may be traced continuously from Loch 
Gainmich along the base of Barkeval and Allival, and similar rocks appear at intervals 
along the same line round the eastern base of the hills. Immediately above this belt of 
felsitic protrusions comes the great body of gabbro. It will be observed that here, as in 
Skye, the base of the gabbro-mass presents a horizon on which injections of acid rocks 
have been particularly abundant. If the breccias are not the result of rock-crushings 
during Palaeozoic time, but are really due to volcanic explosions during the Tertiary period, 
they are evidently older than the eruption of the gabbros. They might be compared 
with the agglomerate-necks through which the youngest eruptive bosses of Skye have 
made their way ; but in their case the component materials have been derived from the 
surrounding platform of ancient rocks, and not from subterranean lavas. 




v 1 1 









Fig. 40. — View of Allival, Rum, sketched from the base of the north-east side of the cone. 



For my present purpose, however, the chief point of importance is the structure of 
the gabbro mass that springs from that platform into the great conical hills of Rum. 
The accompanying sketch (fig. 40) will convey a better idea of this structure than a 
mere description. At the base, immediately above the felsite just referred to, bedded 
dolerites mark their appearance, much intersected with veins from the siliceous rock. 
Veins and dykes of basalt also cut all the rocks here, the newest being those which run 
in a N.W. direction. The lowest beds of dolerite are succeeded by overlying sheets of 
coarser dolerites, gabbros, troctolites, Sec, which are as regular in their thickness and 
continuity as the ordinary basalts of the plateaux. The band of light-coloured troctolite, 
in particular, about twenty to thirty feet thick, which has been already referred to, 



136 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

can be followed for some distance along the base of the hill as a marked projecting 
escarpment (shown in the foreground of fig. 40). Higher up, other varieties are ranged 
in successive parallel beds, the harder kinds standing out boldly as prominent ribs, while 
the softer crumble into a kind of sand, which forms talus-slopes between the others. 
Alternations of this nature are continued up to the very top of the mountain. The 
beds are nearly flat, but dip slightly into the interior or towards the south-west. 

But not only are the gabbro and associated rocks disposed in beds differing from each 
other in pctrographical characters. The same parallel arrangement may be traced even in 
the internal structure of some of the individual beds. The most remarkable example of 
this nature which I have found is presented by the band of light-coloured troctolite 
just referred to. This rock at once arrests attention by its laminar structure. Indeed, 
hand-specimens of it, as I have said, might readily pass for pieces of schistose limestone. 
It consists of successive layers, which on the weathered surface divide it into beds almost 
as regular as those of a sandstone, each bed being further separated into laminae marked 
off by the darker and lighter tints of their mineral constituents. The darker layers consist 
of olivine, and the lighter of plagioclase. This segregation here and there takes the form 
of rounded masses, where the minerals are more indefinitely gathered together, and the 
affinity of the rock with intrusive sheets is further displayed by the occurrence of 
abundant nut-like aggregates of pale green olivine. Examined under the microscope, this 
flow-structure is admirably seen, the lath-shaped felspars being drawn out parallel to the 
planes of movement, and giving thereby the peculiarly schistose structure which is so 
deceptive. 

The bedded arrangement of the gabbros is conspicuous from bottom to top of the great 
eastern cones, as shown in figs. 39 and 40, and the dip is gently inw r ards to the W. or 
SW. On the west side also, beyond Loch Sgathaig, a distinct bedding may be traced, 
the inclination being here once more inwards or to the E. But from Glen Harris and 
the base of Askival this structure becomes less marked, and gradually disappears. There 
is thus a central or southern amorphous region, while round the margin towards the north 
and east the rock appears in frequent alternating beds. 

It is clear that in the broad features of their architecture, the hills of Rum follow 
closely the plan shown in the Cuillin Hills of Skye. In each case, there is a structureless 
central region, where the rocks are more coarsely crystalline, and an outer marginal belt, 
where they assume a bedded character and become finer in grain. But, unfortunately, in 
Rum denudation has gone so far that no connection can be traced on the ground between 
the gabbros and the plateau-basalts. As already stated, the latter rocks have been almost 
entirely stripped off from the platform of sandstones and schists which they undoubtedly 
at one time covered, and the few outliers of them that remain lie at some little distance 
from the margin of the gabbro area. Nevertheless, we are not without some indications 
of them underneath the gabbros. I have alluded to the basalts that lie at the base of 
the eastern cones. As we follow the bottom of the gabbro southward round the flanks of 
the hills, dull compact black shattery basalts, with a white crust, appear from under the 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 137 

more crystalline sheets. These at once remind one of the altered basalts of Skye and 
Mull. On the west side also, beds of basalt emerge from under the gabbro, but they 
have been so veined and indurated by the granophyre of that district, that their relations 
to the gabbro are somewhat obscured. If we could restore the lost portions of the 
plateau, I believe we should find the gabbros of Eum resting on part of the volcanic 
plateau, and some of the gabbro-beds prolonged as intrusive sheets between the beds of 
basalt. 

(c) Ardnamurchan. — The promontory of Ardnamurchan reveals as clearly as the 
flanks of the Cuillin Hills, though in a less imposing way, the relations of the gabbros 
to the plateau-basalts. From the southern shore at Kilchoan to the northern shore at 
Kilmory, bedded basalts, of the usual type, amygdaloidal and compact, weathering into 
brown soil, may be followed along the eastern slopes of the hills, resting upon the 
quartzites and schists of western Argyleshire. These rocks are a continuation of those 
that cap the ridges further to the south-east and cross Loch Sunart into Morven. They 
dip westwards, and followed upwards in that direction, they soon present the usual 
marks of alteration. They weather with a white crust and become indurated and 
splintery. Sheets of dolerite with many veins and dykes of basalt run between and 
across them. Bands of gabbro make their appearance, and these, as we advance 
westwards, increase in number and in coarseness of grain until this rock, in its 
characteristically amorphous form, constitutes practically the whole of the promontory 
from Meall nan Con to the lighthouse. Many admirable sections may be seen on the 
coast- cliffs and in the rugged interior, showing how prone the gabbro in its central 
structureless portions is to develop segregation-veins. Large crystals of its component 
minerals run in bands or ribbons across the rock, and traces of a peculiar arrangement 
may be found to which I shall refer in the following account of the similar rocks of Mull. 

(d) Mull. — In the island of Mull, the conclusions to which the geology of the other 
volcanic districts leads us as to the position of the gabbros in the series of volcanic 
phenomena, are confirmed and completed. The first geologist who appears to have 
observed the relation of these rocks in that island was Jameson, who classed them 
under the old name of " greenstone," including in the same designation rocks now termed 
dolerites and gabbros. He ascended one of the hills above Loch Don, probably Mainnir 
nam Fiadh (2483 feet), -which he found to consist of "strata of basalt and greenstone," 
with some basalt-breccia or tuff and a capping of basalt. He speaks of the " singular 
scorified-like aspect " of the weathered greenstone — a description which applies to some 
of the coarser gabbro bands of that locality. But he appears to have recognised the 
general bedded arrangement of the rocks up even to the summit of the hill.* 

It was not, however, until the visit of Professor Zirkel in 1868, that the true 
petrographical characters of the gabbro of Mull were recognised. The same observer also 
remarked that the rock is regularly interstratified with the basalt.t Professor Judd, 
as already stated, has supposed the gabbros to be the deep-seated portion of the masses 

* Mineralogy of the Scottish Isles, i. p. 205. t Zeitsch. Deutsch. Geol. Gesellsck, xxiii. (1871) p. 58. 



138 DR GE1K1E ON THE HISTORY OF VOLCANIC ACTION 

which when poured out at the surface became the plateau-basalts, and he represents 
them in his map and sections of Mull as ramifying through the granitic rocks.'"" 

In Mull some peculiarities in the arrangement of the gabbro are better developed 
than elsewhere. Instead of forming a huge boss with an amorphous centre and a fringe 
of intrusive sheets, as in Skye and Ardnamurchan, the rock is distributed in innumerable 
beds or sheets interposed between the plateau-basalts. The area within which this 
chiefly occurs is tolerably well-defined by the difference of contour between the long- 
terraced uplands of the ordinary basalts and the more conical forms of the southern 
group of hills between Loch na Keal and Loch Spelve. The number and thickness of 
the gabbro-sheets increase as we proceed inwards from the basalt-plateau. These sheets 
are specially prominent along the higher parts of the ridge that runs northwards from 
the northern end of Loch Spelve, and along the west side of Glen Forsa. But they swell 
out into the thickest mass in the south-western part of the hilly ground, where from 
above Craig, in Glenmore, they cross that valley, and form the rugged ridge that rises 
into Ben Buy (2354 feet), and stretches eastward to near Ardara. It is in this 
southern mass that the Mull gabbro approaches nearest in general characters to the bosses 
of the other districts. But even there, its true intercalation above a great mass of 
bedded basalt may readily be ascertained in any of the numerous ravines and rocky 
declivities. 

One of the best lines of section for exhibiting the relations of the rocks is the declivity 
to the west of Ben Buy and Loch Fhuaran. Ascending from the west side, we walk over 
successive low escarpments and terraces of the plateau-basalts with a gentle inclination 
towards N.E. or E. These rocks weather in the usual way, some into a brown loam, 
others into spheroidal exfoliating masses. But as we advance uphill, they gradually 
assume the peculiar indurated shattery character already referred to. The soft earthy 
amygdaloids become dull splintery rocks, in which the amygdules are no longer sharply 
defined from the matrix, but rather seem to shade off into it, sometimes with a border of 
interlacing fibres of epidote. The compact basalts have undergone less change, but they 
too have become indurated, and generally assume a white or grey crust, and none of 
them weather out into columnar forms. Strings and threads full of epidote run through 
much of these altered rocks. Abundant granophyric and felsitic veins traverse them. 
Sheets of dolerite likewise make their appearance between the basalts, followed further 
up the slope by sheets of gabbro until the latter form the main body of the hill. 

On the north side of the same ridge, similar evidence is obtainable, though somewhat 
complicated by the injections of granophyric and felsitic veins and bosses, to which more 
detailed reference will afterwards be made. But the altered basalts, with their amygda- 
loidal bands and their intercalated basalt tuffs and breccias, can be followed from the 
bottom of the glen up to a height of some 1700 feet, above which the main gabbro mass 
of Ben Buy sets in. Many minor sheets of dolerite and gabbro make their appearance 
along the side of the hill before the chief overlying body of the rock is reached. Some 

* Quart. Jour. GeoJ. Soc, xxx. (1874). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



139 



of these can be distinctly seen breaking across or ending off between the bedded basalts 
which here dip gently into the hill (fig. 41). A conspicuous band of coarse basalt- 
agglomerate, containing blocks of compact and amygdaloidal basalt a yard or more in 
diameter, shows by the excessive induration of its dull-green matrix the general alteration 
which the rocks of the basalt-plateau have here undergone. An almost incredible 
number of veins of fine basalt, porphyry, and felsite has been injected into these rocks — 
a structure which is precisely a counterpart of what occurs under the main body of gabbro 
in Skye, Ardnamurchan, and Rum. 

The gabbro mass of the Ben Buy ridge is thus undoubtedly a huge overlying sheet, 
which probably reaches a thickness of at least 800 feet. It seems to descend rather 
across the bedding into the hollow of Glen More, and possibly its main pipe of supply 
lay in that direction. Being enormously thicker than any other sheet in the island, it 
exhibits the crystalline peculiarities which are so well developed in the central portions 
of the larger bosses of gabbro. It presents more coarsely crystalline varieties than appear 
in the thinner sheets, some portions showing crystals of diallage and felspar upwards of 




Fig. 41.— Altered Plateau-Basalts invaded by Gabbro, and with a Dyke of prismatic Basalt cutting both rocks, North 
Slope of Ben Buy, Mull, aa, amygdaloidal basalt, much altered; b, gabbro; c, finely prismatic basalt. 

an inch in length. It likewise contains admirable examples of segregation-structure, 
which, as in Skye and elsewhere, is best developed where the texture becomes especially 
coarse. These veins or seams, in which the constituent minerals have crystallised out in 
more definite and conspicuous forms, here and there succeed each other so quickly as to 
impart a kind of bedded or foliated look to the body of rock in which they occur, recalling 
the aspect of some coarsely crystalline granitoid gneiss. Occasionally, on the exposed 
faces of crags, portions of such veins are seen to be detached and enveloped in the finer 
surrounding matrix. This pseudo-stratification is to be distinguished from another struc- 
ture in which thick belts or bands of coarser and finer texture alternate, and give an 
appearance of bedding to the mass. These bands run generally parallel with beds of 
highly indurated basalt, which appear to be separated portions of the ordinary rocks of 
the plateau. They may be taken to indicate that the thick sheet of Ben Buy is not 
the result of one but of many uprises of gabbro. 

Of the thinner sheets of dolerite and gabbro little need here be said. I have referred 
to their great abundance in the range of eastern hills that rise from the Sound of Mull 



140 DR GEIKIE ON THE HISTORY OE VOLCANIC ACTION 

between Loch Spelve and Fislinish Bay. Though obviously intrusive, they lie on the whole 
parallel to the bedding of the basalts. The latter rocks exhibit the usual dull indurated 
shattery character which they assume where the gabbro has invaded them, and which 
gradually disappears as we follow them down hill away from the intrusive sheets to the 
shores of the Sound. They dip towards the centre of the hill group, that is to S. W. in the 
ridge of Mainnir nam Fiadh, Dun da Ghaoithe, and Beinn Meadhon, the angle increasing 
southwards to 15°-20°, and at the south end reaching as much as 35°-40°. Some fine 
crags of gabbro and dolerite form a prominent spur on the east side of the ridge of Ben 
Talaidh, in the upper part of Glen Forsa. These consist of successive sheets bedded with 
the basalts, and dipping S.W. A large sheet stands out conspicuously on the north front 
of Ben More, lying at the base of the " pale lavas," and immediately above the ordinary 
basalts, and circles round the fine corry between Ben More and A'Chioch, some of its domes 
being there beautifully ice-worn. This is the highest platform to which I was able satis- 
factorily to trace any of the intrusive sheets of Mull. Another dyke-like mass emerges 
from beneath the talus slopes of A'Chioch, on the southern side, and runs eastward across 
the col between the Clachaig Glen and Loch Scridain. 

§ 3. Structure of the Gabbro Areas. 

We are now in a position to draw, from the observations which have here been given 
regarding the different areas of gabbro in the Tertiary volcanic region of Britain, some 
general conclusions with respect to the type of geological structure which they illustrate. 

1. No evidence exists to show that the extruded masses of gabbro ever communicated 
directly with the surface. They never exhibit the cellular, slaggy and other structures so 
characteristic of surface-flows. They are, on the whole, free from included masses of 
breccia and agglomerate, though portions of such rocks have been detected among the 
boulders derived from one part of the Cuillin Hills. If the gabbro-bosses ever were con- 
tinuous with sheets of rock emitted above ground, all such upward continuations have 
been entirely removed. In any case, we may be quite certain that in an outburst at 
the surface the rock would not have appeared in the form of a coarsely crystalline or 
granitoid gabbro. 

2. The crystalline structures of the gabbros point unmistakably to slow cooling and 
consolidation at some considerable depth beneath the surface. The most coarsely- 
crystalline varieties, and those with the best developed segregation-veins, occur in the 
largest bodies of rock, where the cooling and consolidation would be most prolonged.* 

3. From the occurrence of bands and more irregular portions of considerably different 
texture and even mineralogical comj)osition, it may be confidently inferred that even 
what appears now as one continuous mass was produced by more than one eruption. 

4. In every case there would necessarily be one or more pipes up which the igneous 
materia] rose. These channels might be supplied by wider parts of fissures, such as those 
filled by the dykes. But more probably they were determined by older vents, which had 

* On this subject, see the papers by Professor Judd already cited. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 141 

served for the emission of the plateau-basalts and their pyroclastic accompaniments. 
There can be no doubt that some of these vents afforded egress for the subsequent eruption 
of granitoid rocks. In the case of the gabbros, however, they seem to have been generally 
concealed by the tendency of these rocks to spread out laterally. Denudation has cut 
deeply into the gabbro-masses, but not deep enough to isolate any of the pipes from the 
material which issued from them, so as to leave solitary necks like those in and around 
the basalt-plateaux. In Skye, where the central core of gabbro is largest and most 
completely encircled, we cannot tell how much of it which is amorphous and resembles 
what might be supposed to be the material filling the actual vent, really lies above the 
true pipe or pipes, and has spread out on all sides from the centre of eruption. All that 
we know is that round the margin of the gabbro we can reach horizons below that rock, 
and see that it lies as a cake or series of cakes upon the plateau-basalts. The actual pipe 
of supply must lie further inward, away from the margin, and may be of comparatively 
small diameter. 

5. From the central pipe or group of pipes which rose from the platform of older 
rocks into the thick mass of the basalt-plateaux, successive sheets of dolerite and gabbro 
were forced outward between the layers of basalt. This took place all round the orifices 
of supply, on many different horizons, and doubtless at many different times. In some 
cases, the intrusive sheets were injected into the very bottom of the basalts, and even 
between these rocks and the older surface on which they rested. This is particularly the 
case in Rum, where the gabbro-cones spring almost directly from the ancient grits, schists, 
and sandstones on which they rest. The intrusive sheets have likewise found egress at 
every higher platform in the basalt-series, up at least to the base of the pale group in 
Mull — that is, through a continuous pile of more than 2000 feet of bedded basalt. But 
the intrusion did not proceed equally all round an orifice. At all events, the progress of 
denudation has revealed that on one side of a gabbro area the injected portions may occur 
on a lower stratigraphical level than they do on the opposite side. At the Cuillin Hills, 
for example, the visible sheets of dolerite and gabbro to the north of Coire na Creiche 
begin about 1600 feet above the sea, which must be much more than that distance above 
the bottom of the basalts. On the south-east side, however, they come down to the 
Torridon sandstone at Loch Scavaig ; that is to say, their lowest members lie about 
the base of the bedded basalts, or more than 1600 feet below those on the opposite 
margin. 

6. The uprise of so much igneous material in one or more funnels, and its injection 
between the beds of plateau-basalt, would necessarily elevate the surface of the ground 
immediately above, even if we believe that surface to have been eventually disrupted and 
superficial discharges to have been established. If no disruption took place, then the ground 
would probably be upraised into a smooth dome, the older lavas being bent up over the 
cone of injected gabbro until the portion of the plateau so pushed upward had risen some 
hundreds of feet above the surrounding country. The amount of elevation, which would 
of course be greatest at the centre of the dome, might be far from equable all round, one 

VOL. XXXV. PAET 2. T 



14-J 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



side being pushed up further or with a steeper slope than another side. But even in the 
case of the Cuillin Hill area, it is conceivable that the total uplift produced at the surface 
a gentle inclination of no more than 8° or 10°. 

It is along the periphery of a gabbro area that we may most hopefully search for 
traces of this uplift. But unfortunately it is just there that the work of denudation has 
been most destructive. There appears also to have been a general tendency to sagging 
subsequent to the gabbro protrusions, and the inward dip thereby produced has probably 
been instrumental in effacing at least the more gentle outward inclinations caused by the 
uprise of the eruptive rock. In one striking locality, however, to which I have already 
referred, the effects of both movements are, I think, preserved. The basalt-plateau 
of Strathaird, which in its southern portion exhibits the ordinary nearly level bedding, 
dips in its northern part at an unusually steep angle to the N.W., towards the gabbro 
mass of Blath Bheinn. But before reachiDg that mountain the basalts, much interbanded 
with sheets of dolerite and gabbro, suddenly bend up to form the prominent eminence of 




a c a 

Fig. 42. — Theoretical representation of the structure of one of the Gabbro Bosses of the Inner Hebrides, a, platform of 
older rock on which the bedded basalts (b) have been poured out ; c, gabbro. 



An Stac, where they dip rapidly towards S.E. and S. (fig. 37). This steep dip away from 
the central mass of gabbro, is repeated in the hills to the north, where the beds are 
inclined to N.E., the angle gradually lessening northwards till they are truncated by 
the granophyre of Strathmore. The theoretical structure of one of the gabbro bosses is 
represented in fig. 42. 

7. The injection of so much igneous material among the bedded basalts has induced 
in these rocks a certain amount of contact metamorphism. I have referred to it as 
showing itself in the field as a marked induration, the rocks becoming closer grained, 
dull, and splintery, weathering with a grey or white crust, while their amygdules lose 
their definite outlines, and epidote and calcite run in strings, veins, and patches through 
many parts of the rocks.* The microscopic characters of the altered basalts are described 
at p. 167. 

* Many years ago I was much struck with the evidence of alteration in the igneous rocks of Mull, and referred to 
it in several papers, Proc. Roy. Soc. Edin. (1866-67), vol. vi. p. 73; Quart. Jour. Geol. Soc, xxvii. (1871) p. 282, note. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 143 

The structure and history of the gabbro bosses of the Inner Hebrides find a close 
parallel in those of the Henry Mountains of Southern Utah, so well described by Mr 
G. K. Gilbert of the United States Geological Survey. In that fine group of mountains, 
rising to an extreme height of 5000 feet above the surrounding plateau, and 11,000 feet 
above the level of the sea, masses of trachyte have been injected between sedimentary 
strata belonging to the Jura-Triassic and Cretaceous systems. These masses, thirty-six 
in number, have consolidated in dome-shaped bodies, termed by Mr Gilbert " laccolites," 
which have arched up the overlying strata, sending sheets, veins, and dykes into them, 
and producing in them the phenomena of contact metamorphism. There is no proof 
that any of these protrusions communicated with the surface, and there is positive 
evidence that most if not all of them did not. The progress of denudation has laid bare 
the inner structure of this remarkable type of hill, and yet has left records of every 
stage in its sculpture. In one place, are seen only arching strata, the process of erosion 
not having yet cut down through the dome of stratified rocks into the trachyte that was 
the cause of their uprise. In another place, a few dykes pierce the arch; in a third, where 
a greater depth has been bared away, a network of dykes and sheets is revealed ; in a 
fourth, the surface of the underlying " laccolite " is exposed ; in a fifth, the laccolite, 
long uncovered, has been carved into picturesque contours by the weather, and its original 
form is more or less concealed.* 

The gabbro " laccolites " of the west of Scotland belong to an older geological period 
than those of Utah, and have, therefore, been longer subject to the processes of 
denudation. They have been enormously eroded. The overlying cover of basalt has 
been stripped off from them, though from the escarpments beyond them it is not difficult 
in imagination to restore it. In Eum it has been so completely removed, that only a few 
fragments remain at some distance from the cone of gabbro which now stands isolated. 
In Ardnamurchan, and still more in Skye, the surrounding plateau of basalt remains in 
contact with the gabbro bosses. But in Mull, where the plateau basalts reach now, and 
perhaps attained originally a greater thickness than anywhere else, they have protected 
the intrusive sheets, which are less deeply cut away there than in any of the other 
districts, and no great central core of gabbro has yet been uncovered. 

IV. THE ACID KOCKS. 

We now come to the consideration of the last and in some respects the most singular 
phase of volcanic action during Tertiary time in Britain. Hitherto all the igneous rocks 
that have been under consideration in this memoir, whether injected below or poured 
out at the surface, have been of basic, some of them indeed, like the peridotites, of ultra- 
basic character. But we now encounter a great series, every member of which is more 
or less decidedly acid, and in which the excess of silica is very commonly visible to the 

* " Geology of the Henry Mountains," by G. K. Gilbert, U. S. Geographical and Geological Survey of the Rocky 
Mountain Region, 1877. 



144 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

eye in the form of free quartz. While in chemical composition there is the strongest 
contrast between this series and the rocks hitherto under discussion, there are also 
marked differences in structure and mode of occurrence. With one solitary exception 
(Scuir of Eigg), all the masses of acid rock are intrusive — that is, they have been injected 
beneath the surface, and therefore record for us subterranean and not superficial mani- 
festations of volcanic action. 

The existence of rocks of this class in the midst of the basic masses has I0112; been 
recognised. They were noticed by Jameson, who described the hills between Loch 
Sligachan and Broadford as composed of " a compound of felspar and quartz, or what imny 
be called a granitel, with occasional veins of pitchstone." # Macculloch gave a fuller 
account of the same region, and classed the rocks as chiefly " syenite" and " porphyry." t 
In Antrim, also, even in the midst of the basalt-tableland, masses of "pitchstone-porphyry," 
" pearlstone-porphyry," and "clay-porphyry" were observed and described.! In more 
recent years Professor Zirkel has given a brief account of the so-called " syenite and 
porphyry" of Mull and Skye§ and the late Professor Von Lasaulx fully described the 
trachyte of Antrim, in which he recognised the occurrence of tridymite.|| 

It is remarkable that up to the present time no connected account of the petrography 
or of the geological relations of this interesting series of rocks has been published. Yet 
we find in it a greater variety of petrographical characters than in any other portion of 
the British Tertiary volcanic rocks. On the one hand, it presents us with thoroughly 
vitreous masses, some of which in their colour, lustre, and microscopic structure remind 
us of recent obsidians. On the other hand, it affords us coarsely crystalline compounds, 
to which we can assign no other name than granite, and which, did we not know their 
geological position, we might class with some of the most ancient eruptive rocks. Between 
these two extremes abundant gradations may be found. 

In dealing with such a series of intrusive rocks, we again encounter the difficulty of 
reaching certainty as to their relative dates of eruption, since in each case all that can 
usually be affirmed is that the intrusive mass is younger than that into which it is 
injected. It is quite possible that protrusions of acid rocks occurred at many intervals 
during the accumulation of the basic masses. We have already seen that in gravels 
near the base of the basalt-plateau of Mull, and in the agglomerates of that island as 
well as of other districts, fragments of siliceous lavas occur. It is quite certain, therefore, 
that at the time when the basalts of the plateaux were emitted, there existed, within 
reach of volcanic explosions, masses of felsitic rocks, fragments from which were shot up 
the funnels of discharge. Whether portions of these rocks were actually intruded 
into the basalt-sheets before the building up of the plateaux was completed, or 
whether in some cases the molten material was poured out in streams of lava at the 

* Miner alogical Travels, ii. 90. 

t Western Isles, see the descriptions of Skye, Mull, and Rum. 

% Berger, Trans. Geol. Soc, iii. (1816) p. 190. 

2 Zeitsch. Deutsch. Geol. Gesellsch., xxiii. (1871) pp. 54, 77, 84, 88. 

|| Tschermak's Min. wntf Petrog. Mittheilungen, 1878, p. 412. 



DURING THE TERTIARY PERIOD IN THE RRIT1SH ISLES. 145 

surface, cannot be decided from the evidence which I have as yet been able to gather. 
All I can affirm at present is — (1) that in no single instance have I met with a trace of 
any acid lava that reached the surface save that of the Scuir of Eigg, which belongs to a 
period long subsequent to the formation of the basalt-plateaux ; and (2) that where the 
relative ages of the rocks can be fixed, the acid protrusions are almost invariably the 
youngest. Indeed, the only exceptions to this rule are the latest basalt-dykes and 
possibly a few basic injections along the margins of the larger gabbro areas. Hence, 
while I frankly admit that the large and varied series of acid rocks, which no doubt 
represents a wide interval of time, may in part belong to comparatively early epochs in 
the protracted volcanic period, the actual available evidence places the emission of these 
rocks as a whole towards the end of the volcanic history. This evidence I shall bring 
forward in full detail, since it necessitates an abandonment of what up to the present 
has been the general belief in regard to the relative ages of the rocks. 

§ 1. Petrography. 

The classification of the rocks which best harmonises the field-evidence and the 
detailed study of their mineralogical composition, is one which arranges these volcanic 
protrusions into two series. In the first, the orthoclase is sanidine, and the rocks range 
from the most vitreous pitch stone through perlitic and spherulitic varieties to quartz- 
trachyte. In the second series, which embraces by far the largest proportion of the whole, 
the orthoclase is always turbid, and in this respect as well as in many others the rocks 
remind us rather of ancient eruptive masses than of those which have appeared in 
Tertiary time. They range from flinty felsitic varieties, which are obviously devitrified 
glasses through different textures of quartz-porphyry into granophyre, and finally into 
granite. As I have been unable to recognise any essential difference of structure and 
composition between these acid Tertiary rocks and those of far earlier geological time, I 
give them the names which no petrographer would hesitate to apply to them if they were 
of Palaeozoic age. It has long appeared to me that these rocks furnish conclusive 
evidence of the misleading artificiality of any petrographical nomenclature in which 
relative antiquity is made an essential element of discrimination. 

1 . Pitchstone and Trachyte Series. 

These rocks, though distributed over a tolerably wide area, never occur in the large 
masses characteristic of the felsitic and granophyric series. They almost always appear 
as veins, and usually in the vitreous condition, the only exceptions yet known being the 
bosses of trachyte which rise here and there through the Antrim basalt-plateau. 

Pitchstone. — This rock is found in veins or dykes which rise through different 
geological formations up to and including the great granophyre bosses of the Inner 
Hebrides. It also in one solitary example occurs as a lava-stream, or rather a succession of 
streams, piled over each other in the ancient river-bed of the Scuir of Eigg. It varies in 



14G DR 'GETKIE ON THE HISTORY OF VOLCANIC ACTION 

colour from a deep jet-black or raven-black to a pale bottle-green, and in lustre from an 
almost glassy obsidian-like to a dull resinous aspect. Occasionally it assumes a dull 
felsitic texture, owing to devitrification, and also a finely splierulitic structure. Some 
varieties appear to the naked eye to be perfectly homogeneous, others become porphyritic 
by the appearance of abundant sanidine crystals. 

The microscopic structure of the British pitchstones has only been partially worked 
out. The beautiful feathery microlites of the Arran dykes, first made known by David 
Forbes, and subsequently described by Zirkel, Allport, and others, are well known objects 
to geological collectors. But no one has yet attempted to investigate the group as a 
whole. I have placed my tolerably large collection of specimens and their slides in the 
hands of Dr Hatch, from whom we may expect before long a memoir on this interesting 
and still little known group of rocks. In the meantime, he has furnished me with 
some preliminary notes on the slides, from which I make the following generalised 
summary. 

At the one end of the pitchstone group we have a nearly pure glass, with no microlites, 
and only a few scattered crystals of sanidine, quartz, augite, or magnetite. The glass in 
thin slices is almost colourless, but generally inclines to yellow, sometimes to dark-grey. 
Some varieties of the rock are crowded with microlites, in others these bodies are 
gathered into groups, the glass between which is nearly free from them. Among the 
minerals that have been observed in this microlitic form are sanidine, augite, hornblende 
(forming the beautiful green feathery or fern-like aggregates in the Arran pitchstones), 
and magnetite. Sometimes the rudimentary forms appear as globulites or as belonites, 
but more commonly as dark trichites. Among the more definite mineral forms are 
grains of sanidine, quartz, and augite. The porphyritic crystals are chiefly sanidine, 
augite, and magnetite, but plagioclase occasionally occurs. The development of spheru- 
lites is well seen in a few of the slides, and occasionally perlitic structure makes its 
appearance. At the Scuir of Eigg, bands of a dull felsitic pitchstone occur, which under 
the microscope show that the glass has been so devitrified as to assume a cryptocrystalline 
structure. 

Quartz- Trachyte. — This rock has not yet been noticed in any other district than in 
Antrim, where it rises in occasional bosses among the plateau- basalts. It is best exposed 
at the Tardree and Carnearny Hills, where it has long been quarried. Its petrographical 
characters were fully described by Von Lasaulx, who found the rock to be a typical 
quartz-trachyte rich in tridymite, and containing large crystals of glassy sanidine, isolated 
narrow laths of plagioclase (probaby andesine), grains of smoky-grey quartz, partly 
bounded by di-hexahedral faces, and a few scattered flakes of a dark-coloured mica. The 
ground mass is microgranitic, and under a high power is resolvable into a confused 
aggregate of minute microlites of felspar, with interstitial quartz-granules.* 

* Tschermak's Min, und Pet. Mittheil, 1878, p. 412. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 147 

2. Felsite, Quartz-Porphyry, Granophyre, and Granite Series. 

Felsite and Quartz-Porphyry. — Under the general name of felsite, I class an abundant 
group of rocks, which macroscopically vary in texture from flinty or horny to dull finely 
granular, and in colour from white through shades of grey, buff, and lilac, to black, 
generally with porphyritic felspars and blebs of quartz. Where these porphyritic 
enclosures increase in size and number, the rocks cannot be distinguished from ancient 
quartz-porphyries, and I have preferred to call them by that name. 

In no single instance have I found any vitreous variety among them, nor any 
remnant of true glass in their minute structure. But that many, if not all of them, were 
originally glasses can hardly be doubted. They often exhibit the most beautiful flow- 
structure, the laminae being distinctly visible to the naked eye as they curve round the 
porphyritic crystals of earlier consolidation. Sometimes indeed this structure has been 
so strongly developed as to cause the rock to weather along the planes of flow and to 
break up into thin slabs. The passage of the original glass into a lithoid condition does 
not seem to have been accompanied with the development of those well-marked types of 
microlites so characteristic of the pitchstones. On the contrary, I have never detected 
any other modification than that confused and indefinite aggregate which is known as 
felsitic. Occasionally a spherulitic structure may be observed. More frequently the 
peculiar radially-fibrous aggregation of quartz and felspar presents itself, which is the 
characteristic structure of the granophyres. There is thus a gradation from ordinary 
felsites and quartz-porphyries through granophyric varieties into perfect granophyres. 

The felsites and quartz-porphyries present many of the structures of rhyolites, and 
would in fact be classed by many petrographers under that name. But I think it better 
to keep the term rhyolite for those acid lavas wherein the felspar occurs as crystals of 
sanidine, which, together with quartz, are embedded in a microcrystalline felsitic or 
vitreous ground-mass. 

There is here again an obvious relation between lithological texture and geological 
position. Where the acid rocks have been injected into narrow chinks and fissures, they 
are finer in grain than in the centre of large masses, and have generally consolidated as 
veins or dykes of felsite or quartz-porphyry. Where they have accumulated in larger 
bosses, as in Mull and Skye, they have taken the form of granophyres or granites. 
Along the margins of these bosses, where the conditions of cooling and crystallisation 
more nearly resembled those in the fissures, the rocks are finer in texture, and not 
unfrequently assume the felsitic or porphyritic aspect, and even show a more or less 
perfect flow-structure. 

Granophyre. — This term, which is here used in the sense employed by Rosenbusch 
(but without his limitation of it to pre-Tertiary rocks), embraces undoubtedly the most 
characteristic and abundant rocks among the acid protrusions of the Inner Hebrides. 
These vary in texture from a fine felsitic or crystalline-granular quartz-porphyry, 
in the ground-mass of which porphyritic turbid felspar and quartz (sometimes bi- 



148 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

pyramidal) may generally be detected, to a granitoid rock of medium grain, in which 
the component dull felspar and clear quartz can be readily distinguished by the 
naked eye. Throughout all the varieties of texture there is a strong tendency to the 
development of minute irregularly-shaped cavities, which here and there give a carious 
aspect to the rock. That these cavities, however, are part of the original structure of 
the rock, and are not due to mere weathering, is shown by the well-terminated crystals 
of quartz and felspar which project into them. On a small scale, it is the same structure 
so characteristic of the granite of the Mourne Mountains and of parts of that of Arran. 

Examined under the microscope, a normal specimen of the granophyre of the Western 
Isles presents a holocrystalline ground-mass, which fills all the interspaces between the 
crystals of earlier consolidation. This ground-mass consists of an aggregate of clear 
quartz and turbid orthoclase, arranged in the structure known as micropegmatite. In 
some parts these two minerals are grouped in alternate parallel fibres, diverging from the 
surface of the enclosed crystals, which are thus more or less completely surrounded by a 
radially fibrous mass. In other parts, the felspar forms a kind of network, the meshes of 
which are filled up with quartz. Through the ground-mass are scattered crystals of clear 
quartz and dull orthoclase, generally with some ferro-magnesian or other additional 
constituent, usually somewhat decomposed. In some varieties Dr Hatch has found an 
abundant brown mica, as in the rock at Camas Malag, Skye. In others, a pyroxene occurs, 
which he finds in minute greenish grains, sometimes completely inclosed in the quartz. In 
a third variety the dark constituent is hornblende, the most remarkable example of which 
is one to be seen at Ishriff, in the Glen More of Mull, where the ferro-magnesian mineral 
takes the form of long dirty-green needles, conspicuous on a weathered surface of the 
rock. A fourth variety is distinguished by containing plagioclase in addition to or instead 
of orthoclase. In the rock of the sheet forming Cnoc Carnach, near Heast, in Skye, Di- 
ll atch has observed both orthoclase and plagioclase scattered through a fine micro- 
pegmatitic ground-mass, and in a part of the boss at Ishriff he has found the rock to be 
composed mainly of plagioclase, in a micropegmatitic ground-mass of quartz and felspar, 
with a few scattered grains of a pale brown augite and grains of magnetite. A fifth 
variety is marked by the prominence of the crystals of quartz and felspar of earlier 
consolidation, and the fineness of grain in the surrounding micropegmatitic ground-mass, 
whereby a distinct porphyritic structure is developed. Eocks of this kind are macro- 
scopically like ordinary quartz-porphyries. 

The granophyres occur sparingly as veins or dykes. Conspicuous examples of their 
assumption of this form are to be seen in the light-grey veins which break through 
the dark gabbro at the lower end of Loch Coruisk, Skye. More massive and striking are 
the great dykes that run up the basalt-terraces on the north side of Loch Sligacban. In 
the form of sheets intruded between the Jurassic strata, or between them and the base of 
some overlying series now removed, the granophyres (having the general aspect of quartz- 
porphyries) play an important part in the geology of Strath, in Skye. But it is as bosses 
that the granophyres attain their largest and most characteristic development, their 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 149 

greatest area being in the groups of the Eed Hills of Skye, between Loch Sligachan and 
Strath. 

Microgranite. — This name is applied to certain intrusive masses, which macro- 
scopically may be classed with the quartz-porphyries and felsites, but which micro- 
scopically are found to possess a holocrystalline granitic ground-mass of quartz 
and orthoclase, through which are scattered porphyritic crystals of the same two 
minerals, sometimes also with plagioclase, augite, magnetite, or apatite. Rocks of this 
type do not appear to be abundant. They occur as dykes and bosses, but occasionally 
also as sheets. I have collected them from Skye, Rum, and Ardnamurchan. 

Granite. — That there are true granites among the acid rocks of the Tertiary volcanic 
series can no longer be doubted. As in their macroscopic characters the more coarsely 
crystalline granophyres are not to be distinguished from granites, and, as their dark 
ferro-magnesian constituent is generally hornblende, they were called by the older petro- 
graphers "syenite"; that is, granite with hornblende instead of mica. In many of the 
granophyres, the microscope reveals transitional stages to granite. The peculiar micro- 
pegmatitic ground-mass may be observed so reduced in amount as only to appear here 
and there between the other minerals which are grouped in a granitic structure. From 
this condition, one step further carries us into a true granite, from which all trace of the 
granophyric character has disappeared. Such gradations may be traced even within short 
distances in the same boss of rock. Thus, portions of the interior of the boss of Beinn- 
an-Dubhaich, Skye, possess a thoroughly granitic arrangement of their component 
minerals, while a specimen taken from near the edge on the shore of Camas Malag, shows 
the appearance of the granophyric ground-mass. But, though the large bosses are 
usually somewhat coarsely crystalline in the centre, and tend to assume finer felsitic 
textures around their borders, as was observed long ago by Oeynhausen and Von 
Dechen,* the granitic structure is sometimes exhibited even at the very edge, and not 
only so, but in the dykes that protrude from the bosses into the surrounding rocks. 
Thus the Beinn-an-Dubhaich mass, at its margin on Camas Malag, sends a vein into the 
surrounding limestone, but though more close-grained than the main body of the rock, 
this vein is neither felsitic nor granophyric, but truly granitic in structure. 

So far as I have observed, the true granites contain a brown mica and also a little 
hornblende, both visible to the naked eye, but generally somewhat decomposed. These 
rocks are thus hornblende-biotite-granites (amphibole-granitites of Rosenbusch). They 
may be defined as medium-grained aggregates of quartz, orthoclase (also plagioclase), 
biotite, and hornblende, with sometimes magnetite, apatite, epidote and zircon. Dr 
Hatch informs me that he finds that in some instances (Beinn-an-Dubhaich) the 
quartz contains minute inclusions (glass ?), bearing immovable bubbles with strongly 
marked contours ; while in others (Beinn-na-Chro, Skye), this mineral is full of liquid 
inclusions with bubbles, sometimes vibratile, sometimes fixed. He remarks that the 
quartz and felspar have consolidated almost simultaneously, but that in some instances 

* Karsten's Archiv, i. p. 89. 
VOL. XXXV. PAKT 2. U 



150 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

(Marsco, Glen Sligachan) there are isolated roughly idiomorphic crystals, of a white, less 
turbid orthoclase, which belong to a slightly earlier consolidation than that of the more 
kaolinised felspar of the rest of the rock. 

With the Tertiary volcanic series of the West Highlands, I have little doubt that the 
granite of the island of Arran should be classed. In 1873 I gave my reasons for believing 
this rock to be of so recent date,* and subsequent microscopic examination has tended to 
confirm this inference by showing the occasional presence in the Arran granite of the 
same granophyric structure so characteristic of the acid rocks of Skye and Mull.t The 
granite of the Mourne Mountains has been shown by the Irish Geological Survey to be 
younger than some of the basic dykes of the south-east of Ireland, and older than 
others.^ And microscopic evidence in this case also links that rock with the granophyres 
of the west of Scotland. 

§ 2. Types of Structure. 

In the history of opinion regarding the relative position of the Tertiary eruptive rocks, 
no point has struck me more than the universal acceptance of what I must now term the 
misconception regarding the place of the acid protrusions. In tracing this mistake to its 
source, we find that it probably arose from the fact that along their line of junction the 
granitoid masses generally underlie the basic. This order of superposition, which would 
usually suffice to fix the age of two groups of stratified rocks, is obviously not of itself 
enough to settle the relative epochs of two groups of intrusive rocks. Yet it has been 
assumed as adequate for this purpose, and hence what can be proved to be really the 
youngest has been placed as the oldest part of the Tertiary volcanic series. 

Macculloch, who showed that his "syenites" and "porphyries" had invaded the 
Secondary strata of the Inner Hebrides, and must therefore be of younger date than these, 
left their relations to the other igneous rocks of the region in a curiously indefinite 
position. He was disposed to regard them all as merely parts of one great series ; and 
seems to have thought that they graduate into each other, and that any attempt to dis- 
criminate between them as to relative age is superfluous. Yet he evidently felt that the 
contrasts of topography which he described could hardly fail to raise the question of 
whether rocks so distinct in outward form did not differ also in relative antiquity. But 
he dismissed the question without answering it, remarking that if there is any difference 
of age between the two kinds of rock, " there appears no great prospect of discovering 
it." § He records an instance of a vein of " syenite " traversing the " hypersthene rock " 
in the valley of Coruisk. " If this vein," he says, " could be traced to the mass of 
syenite, it might be held a sufficient ground of judgment, but under the present circum- 
stances, it is incapable of affording any assistance in solving the difficulty."! Instead, 

* Trans. Edin. Geol. Soc, vol. ii. part 3. 

t See Mr Teall's British Petrography (1888), p. 328. 

X Explanation to Sheets 60, 61, and 71, Geo!. Survey, Ireland, pp. 16, 30. 

§ Western Islands, i. p. 368 ; see also pp. 488, 575, 578. 

|| Op. cit., p. 37 ). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 151 

however, of being a solitary instance, it is only one of hundreds of similar intrusions, 
which can be connected with the general body of granitoid and porphyritic rocks, and 
which put the relative ages of the two groups of rock beyond any further doubt. 

Boue, who knew the geology of some of the extinct volcanic regions of Europe, recog- 
nised the similarity of the Scottish masses to those of the Continent, and classed the 
acid rocks as " trachytes." He saw in each of the volcanic areas of the west of Scotland 
a trachytic centre, and supposed that the more granitoid parts might represent the centres 
in the European trachytic masses. He traced in imagination the flow of the lava-streams 
from these foci of volcanic activity, distinguishing them as products of different epochs 
of eruption, among the last of which he thought that the trachytic porphyries might have 
been discharged. He admitted, however, that his restoration could not be based on the 
few available data without recourse to theoretical notions drawn from the analogy of other 
regions.* 

In the careful exploration of the central region of Skye made by Von Oeynhausen and 
Von Dechen, these able observers traced the boundary between the " syenite " and the 
" hypersthene rock "; and as they found the former lying underneath the latter, they seem 
naturally to have considered it to be the older protrusion of the two.t Principal Forbes 
came to a similar conclusion from the fact that he found the dark gabbro always over- 
lying the light-coloured felspathic masses. | Professor Zirkel also observed the same 
relative position, and adopted the same inference as to the relative age of the rocks. § 
Professor Judd followed these writers in placing the acid rocks before the basic. He 
has supposed the granitoid masses to form the cores of volcanic piles probably of 
Eocene age, through and over which the extrusions of gabbro and the eruptions of the 
plateau-basalts took place. || 

Among the protrusions of acid rocks in the Tertiary volcanic areas of Britain four 
distinct types of structure may be noted, viz. (l) bosses, (2) sills or intrusive sheets, 
(3) veins and dykes, and (4) superficial lava-streams. Of these the first three belong 
entirely to the underground operation of volcanism, the last is the only one which reveals 
the outflow of material at the surface. 

1. Bosses. 

These are irregular protrusions varying in size from knobs measuring only a few 
square yards up to huge masses many square miles in extent, and comprising groups of 
lofty hills. As a rule, their outlines are markedly irregular. Beneath the surface they 
plunge down almost vertically through the rocks which they traverse, but in not a few 
instances their boundaries are inclined to the horizon so that the contiguous rocks seem 

* Essai Gdologique sur VEcosse, pp. 291, 322, 327. 
t Karsten's Archiv, i. p. 82. 
X Edin. New Phil. Jour., xL (1846) p. 84. 

§ Zeitsch. Deutsch. Geol. Gesellsck, xxiii. (1871) pp. 90, 95. He says that the gabbro seems to be the younger rock, 
so far as their relations to each other can be seen. 
|| Quart. Jour. Geol. Soc, xxx. p. 255. 



152 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

to rest against them, and sometimes lie in outliers on their sides and summits. From 
the margins of these bosses veins are given off into the surrounding rocks, sometimes 
only rarely and at wide intervals, in other places in prodigious numbers. 

The rock of which the bosses consist is generally granitoid in texture, passing on the 
one hand, particularly in the central parts, into a truly granitic character, and on the 
other, and especially towards the margin, into granophyre, quartz-porphyry, and various 
compact felsitic varieties, and sometimes exhibiting along the outer edge a more or less 
developed flow-structure. 

Decided contact metamorphism is traceable round the bosses, but is by no means 
uniform even in the same rock, some parts being highly altered, while others, exposed 
apparently to the same influences, have undergone little change. The most marked 
examples of this metamorphism are those in which the Lower Silurian limestone of Skye 
has been converted into a pure white saccaroid marble.* But the most interesting to the 
student of volcanic action are those where the altered rocks are older parts of the volcanic 
series. As the bosses of each volcanic area offer distinctive peculiarities they will here 
be described geographically. 

a. Mull. — Though of comparatively small extent the bosses of the island of Mull 
probably afford to the geologist a larger amount of instruction than those of any 
other district. Especially important is the evidence which they contain of the true 
relations of the acid and basic groups of rocks. They have been laid bare in many 
natural sections, some of which, forming entire hill sides, are among the most astonishing 
in the whole wonderful series which, laid open by denudation, reveal to us the structure 
of these volcanic regions. They lie in two chief areas. One of these extends along the 
northern flanks of the mountainous tract from the western side of Beinn Fhada across 
Loch Ba' to the west side of Glen Forsa. The other occupies for over three miles the 
bottom of Glen More, the deep valley which, skirting the southern side of the chief group 
of hills, connects the east side of the island by road with the head of the great western 
inlet of Loch Scridain. There are other minor areas. One of these extends for about a 
mile along the declivities to the south of Salen, across the valley of the Allt na Searmoin ; 
another occurs at Salen, a third runs along the shore at Craignure. In the interior also, 
many isolated areas of similar rocks, besides thousands of veins, occur in the central group 
of hills and valleys which form the basins of the Glencannel and Forsa rivers. 

The chief northern boss, which for the sake of convenience of reference may be 
called that of Loch Ba', has a length of nearly six miles, with a breadth varying from a 
quarter of a mile to about a mile and a quarter. It descends to within fifty feet of the 
sea-level, and is exposed along the crest of Beinn Fhada at a height of more than 1800 
feet. It chiefly consists of a grey crystalline rock which might readily be identified as 
a granite, but which when examined microscopically is found to possess the granophyric 
structure. But with this distinctly granular-crystalline rock are associated various 

* This marble was 1 elieved to be altered Lias ; but I have proved it by lithological, stratigraphical, and 
pah-contological evidence to be Lower Silurian (Quart. Jour. Geol. Soc, xliv. (1888) p. 62). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



153 



porphyritic and felsitic masses, which pass into it, and are more specially observable along 
its border. An exceedingly compact black quartz-felsite forms its southern boundary, 
runs as a broad dyke-like ridge from the head of the Scarrisdale Water, north- 
eastward across Loch Ba' (fig. 43), and spreads out eastward into a mass more than a 
mile broad on the heights above Kilbeg in Glen Forsa. The sharp line of demarcation 
of this felsite, and its mass and extent, point to different periods of extravasation in the 
Loch Ba' boss. 

The geologist, who approaches this district from the north-east, has his attention 
arrested, even at a distance of several miles, by the contrast between the outer and inner 
parts of the hills that lie to the south-west of Loch Ba'. He can readily trace from 
afar the dark bedded basic rocks rising terrace above terrace from the shores of Loch 
na Keal to form the sea- ward faces of the hills along the southern side of that fjord. 
But he observes that immediately behind these terraces the mass of the rising ground 




Fig. 43. — View of the hills on the south side of the head of Loch 11a Keal, showing the junction of the Granophyre and the 
Bedded Basalts. One bird, the bedded basalts of the Gribon plateau; two birds, the bedded dolerites and basalts of Beinn 
a' Chraig adhering to the northern slope and capping the hill ; three birds, summit of Ben More, with A'Chioch to the 
left and the top of Beinn Fhada appearing in the middle distance between them ; four birds, the granophyre slopes of 
Beinn a' Chraig with the great dyke-like mass of felsite on the left. 



obviously consists of some amorphous rock which weathers into white debris. Nothing 
can be sharper than the contrast of colour and form between the two parts of the hills. 
The bedded plateau-rocks lie as a kind of wall or veneer against a steep face of the structure- 
less interior (fig. 43). Seen from the other or hilly side, the contrast is perhaps even 
more striking. But the astonishment with which it is beheld at a distance becomes 
intensified when one climbs the slopes, and finds that the sheets of dolerite and basalt 
(which from some points of view look quite level, yet dip towards the north-east at a 
gentle angle), are immediately behind the declivity abruptly truncated by a mass of 
granophyre. So little disturbed are they, that one's first impulse is to search for pebbles 
of the granophyre between the basalts, for it seems incredible that the inner rock should 
be anything but a central core of older eruptive material, against and round which the 
younger basic rocks have flowed. But, though the granophyre is so decomposing 



154 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



and covers its slopes with such "screes" of debris, that had the basalts been poured round it, 
they must infallibly have had some of its fragments washed down between their 
successive flows, not a single pebble of it is there to be found. This might not be 
considered decisive evidence, but it is extended and confirmed by the fact that the acid 
rock gives off veins which ramify through the basalts. 

In the bed of the south fork of the Scarrisdale stream, a separate boss of granophyre 
(which under the microscope exhibits in perfection the characteristic structure of this rock), 



"X s - 




\ y,i: y Mm 



Fig. 44. — Section on south side of Cruach T6rr an Lochain, Mull, a, bedded basalts and dolerites ; b, granophyre ; 
c, felsitic band ; dd, veins of felsite traversing the basic rocks. 

protrudes through the basalts in advance of the main mass, and a little higher up on the 
outskirts of that mass narrow ribbons of the granophyre run through the basic rocks. 
The contrast of colour between the pale veins of the intrusive rock and the dark tint of 
the basalts is well shown in the channel of the water. Similar sections may be seen on 
the flanks of Beinn Fhada, especially in the great corry north of Ben More, where the 
granophyre sends a tongue of finer grain between the beds of basalt. On the east side 

of Loch Ba' numerous proofs of similar intrusion 
may be observed. Thus at the east end of Loch 
na Dairidh, where the granophyre has been in- 
truded into the basalts, hand-specimens may be 
obtained showing the two rocks welded together. 
On the slopes of Cruach T5rr an Lochain, where 
the granophyre has a felsitic selvage, the bedded 
basalts are traversed by veins of the latter material 
(fig. 44). A little further east, at the head of 
the Allt na Searmoin, the bedded basalts, some 
of which are separated by slaggy scoriaceous sur- 
faces, are intersected by another protrusion from the compact felsitic porphyry (fig. 45).* 
A mile lower down the same valley a separate mass of granophyre sends out veins into 
the basalts. 

As the posteriority of the granophyre and felsites to the basalts is thus proved, the 
further question remains as to their mode of intrusion. Here and there, especially on 

* This rock appears to the eye as a black finely crystalline-granular felsite. Under the microscope " it presents a 
markedly granulitic structure, consisting mainly of small rounded grains of dirty brown turbid felspar, with isolated 
granules of colourless quartz. Scattered through the rock, or accumulated in patches, are small spherical or drop-like 
granules of a bright green augite (coccolite)." — Dr Hatch. 




Fig. 45. — Section at head of Allt na Searrnoin, Mull. 

a, basalts and dolerites, with slaggy upper surfaces ; 

b, felsite. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 155 

the south-eastern side, between the head of the Scarrisdale river and Loch Ba', the line 
of junction between the two rocks is nearly vertical, but a body of black felsite 
intervenes as a huge wall between the ordinary granophyre and the basalt. On Beinn 
Fhada and Beinn a' Chraig the line of separation, as I have above remarked, is inclined 
outwards, and plunges under the basalts at an angle of 30° to 40°. The terraced basalts and 
dolerites are not sensibly disturbed, but end off abruptly against the steep face of intrusive 
rock. We might suppose that in this case the younger rock had merely carried upward 
the continuation of the beds that are truncated by it. But on the top of the ridge of Beinn 
a' Chraig we find that the outliers which there remain are not portions of the lower 
basalts, but of the upper pale group of Ben More. The same rocks are prolonged on 
the other side of the Scarrisdale Glen, sweep over the summit of Beinn Fhada, and run 
on continuously into the crest of A'Chioch and the upper part of Ben More. The 
granophyre has usurped the place of the lower dolerites and basalts, but has left the 
felspathic lavas of the "pale group" in their proper position. And to make this 
remarkable structure still more clear, sections may be seen on the southern flanks of 
Beinn Fhada, where the upper surface of the granophyre comes down obliquely across 




Fig. 46. —Section on south side of Beinn Fhada, Mull, cm, bedded basalts and dolerites ; 
b, "pale group " of Ben More ; c, granophyre. 

the edges of the lavas, and allows the junction of the basalts and the "pale group" to 
be seen above it (fig. 46). 

Contact metamorphism has been produced around this intrusive boss. It is most 
marked in the outliers that cap Beinn a' Chraig and on the two ridges to the south- 
west. In the field, it is seen to consist in a high degree of induration, the production 
of a shattery irregularly jointed structure, and the effacement of the obvious bedding 
which characterises the unaltered rocks. The microscopic changes will be described on 
a later page, together with those of other districts. 

The position of this eruptive mass, quite a mile broad, breaking through, without 
violently tilting them, more than 1800 feet of the bedded basalts, and then stopping 
short about the base of the " pale group," presents a curious problem to the student 
of geological physics. It at once reminds him of many sections among Palaeozoic 
granites where an eruptive boss has ascended and taken the place of an equivalent 
volume of the surrounding rocks, which, though more or less metamorphosed, are not 
made to dip away from it as from a solid wedge driven upwards through them. In this 
Mull case, however, there are some peculiar features that deserve consideration, for 



156 Dll'GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

they seem to show that here as elsewhere passages for the uprise of the intrusive 
rock were already provided by the presence of volcanic pipes, which, even if filled up 
with fragmentary materials, would no doubt continue to be points of weakness. 
Round the flanks of the Loch Ba' boss, and here and there on its surface, patches 
of intensely indurated volcanic agglomerate may be detected. A little to the south 
of the tarn called Loch na Dairidh, the granophyre is succeeded by the black flinty 
felsite already referred to. This rock in some places exhibits a beautiful flow- 
structure, with large porphyritic felspars, and incloses a great many fragments of 
dolerite and gabbro, varying from the size of a pea up to blocks several inches in 
diameter. Lying on its surface are detached knolls of much altered dolerite, basalt, 
and coarse breccia or agglomerate. On its southern margin one of these patches of 
agglomerate contains abundant fragments of various felsitic rocks, among which are 
pieces of a compact rock with flow-structure like that found in place immediately to 
the north ; also rounded pieces of quartzite, and of compact and amygdaloidal basalt 
wrapped up in a very hard matrix which seems to consist largely of basalt-dust. No 
bedding can be made out in this rock, and the mass looks like part of a true neck. 
Further down the slope the bedded basalts appear. The actual junctions of the different 




e 

Fig. 47. — Section to south of Loch na Dairidh, Mull, a, basalts ; b, dolerites ; c, volcanic agglomerate ; 

d, black felsite ; c, granophyre. 

rocks cannot be satisfactorily traced, but the structure of the ground appears to me to 
be as shown in fig. 47. A patch of similar agglomerate appears a little to the south- 
west of the last section in front of a cliff of the felsite, and seems to be enclosed in 
the latter rock, and other exposures of agglomerate, underlain and intensely indurated 
by the felsite, may be noticed on the ground that slopes towards Loch Ba'. 

That these agglomerates do not belong to the period of the eruption of the grano- 
phyre and felsite, but to that of the bedded basalts, may be inferred from their intense 
induration next the acid rocks, and also from the fact that similar breccias are actually 
found here interposed between the bedded basalts. This is well shown on the hill above 
the Coille na Srbine, where the accompanying section can be seen (fig. 48). The broad 
dyke-like mass of black flinty felsite already referred to runs as a prominent rib over the 
southern end of Beinn a' Chraig into the head of the Scarrisdale glen (see fig. 43). It 
cuts across the bedded basalts, and immediately to the south of where these appear, a thin 
intercalated bed of breccia crops out, of the usual dull-green colour, with abundant frag- 
ments of basalt and many of yellow and grey felsite. 

From these various facts we may, I think, conclude that along the strip of ground now 
occupied by the Loch Ba' boss of granophyre and felsite, there once stood a line or 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



157 



group of small vents, from which, besides the usual basalt-debris, there were ejected many- 
pieces of different felsitic (or rhyolitic) rocks, and that these eruptions of fragmentary 
material took place during the accumulation of the plateau-basalts. The existence of 
these volcanic funnels occasioned a line of weakness of which, in a long subsequent 
episode of the protracted volcanic period, the acid rocks took advantage, forcing them- 
selves upwards therein, and leaving only slight traces of the vents which assisted their 
ascent. 

The second or Glen More boss, instead of rising into hilly ground, is confined to the 
bottom of the main and tributary valleys, and has only been revealed by the extensive 
denudation to which these hollows owe their origin. It begins nearly a mile below 
Torness and extends up to Loch Airdeglais — a distance of almost four miles. Though 
singularly devoid of topographical feature, it exhibits with admirable clearness the 
relation of the granophyres to the gabbros, and thus deserves an important place among 
the tracts of acid rocks in the Western Islands. Its petrographical characters change 



'^^W THTitiYj 





Fig. 48. — Section of junction of south side of Loch Ba' Granophyre boss, with the Bedded Basalts, Mull, a, bedded 
basalts; bb, basalt-tuff and breccia; c, granophyre; d, black felsite; e, coarse dolerite dyke, 30 or 40 feet wide. 



considerably from one part of its body to another. For the most part, it is a true grano- 
phyre, sometimes with orthoclase, sometimes with plagioclase as its predominant felspar. 
At Ishriff, as already stated, it is sprinkled with long acicular decayed crystals of horn- 
blende ; but at the watershed the ferro-magnesian mineral is augite. The surrounding 
rocks are mainly the plateau-basalts, with their intruded sheets of dolerite and gabbro. 

This strip of granophyre sends abundant apophyses from its mass into the dark basic 
rocks around it. Some of the best sections to show the nature of these offshoots are to 
be found on the steep hill-slope which mounts from the watershed in Glen More 
southward into the Creag na h-Iolaire (Eagle's Crag), and thence up into the great 
gabbro ridge of Ben Buy. From the main body of granophyre a multitude of veins 
ascends through the basalts and gabbros from 2 feet or more in breadth down to mere 
filaments. Even at a height of 300 feet up the hill some of these veins are still 3 inches 
broad, and present the usual granophyric structure, though rather finer in grain than the 
general mass of the boss, and sometimes assuming a compact felsitic or spherulitic texture 

VOL. XXXV. PART 2. X 



158 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



at the immediate contact with the surrounding rock. One of the most striking proofs 
of the posteriority of these veins is furnished by the perfect flow-structure they not 
infrequently exhibit along their margins, their long felspar crystals being arranged 
parallel to the walls in lines that follow the sinuosities of the boundary between the two 
rocks (fig. 49). Patches of gabbro and of the indurated basalts may be seen lying on 




Fig. 49. — Mass of dark Gabbro about two feet in diameter traversed by pale veins of Granophyre, 
lying on north slope of Creag na h-Iolaire, Mull, 

the granophyre, from which veins and strings ramify through them (fig. 50). Similar 
veins can be traced upward into the main body of coarse gabbro, forming the ridge of 
Ben Buy. Some of them are of the usual granular granophyric texture, others are dull 
fine-grained porphyries (claystones of the older authors). 

Hence it is evident that the granophyres in Mull have been protruded not only after 




Fig. 50. — Section at Creag na h-Iolaire, Glen More, Mull, showing Basalts and Gabbros resting on and pierced by Granophyre. 
a, much indurated and altered basalts and dolerites ; bb, gabbro ; c, granophyre ; dd, basalt dykes. 



the accumulation of the plateau-basalts, but after these were traversed by the sheets and 
veins of gabbro. The amount of acid rock injected into these older rocks over the 
mountainous part of the island is enormous ; but I reserve further reference to it for the 
section on dykes and veins, for these are the forms in which it chiefly occurs. It should 
be added, that in the localities here referred to basalt-veins and dykes are generally 



DURING THE TERTIARY" PERIOD IN THE BRITISH ISLES. 159 

abundant, cutting through all the other rocks (fig. 50). So numerous are they that the 
geologist ceases to take note of them when his thoughts are engaged upon the problems 
presented by the masses through which they rise. 

b. Small Isles. — In the island of Eigg three small bosses or sheets occur. That 
at the northern end rises through the Jurassic sedimentary rocks, and forms a bold cliff 
from 150 to 200 feet high. It is a light grey granophyric porphyry, with rounded blebs 
of quartz in a micropegmatic base of quartz and felspar. The other two masses, of 
smaller size, cut through the bedded basalts.* 

In the opposite island of Eum, the acid protrusions play a much more important part. 
On the east side of the hills, they occur in sheets at the base of the gabbros; on the west 
side, they form a large tract of hilly ground, which, stretching along the coast line for 
about three and a half miles from the headland of A' Bhrideanaeh to Harris, forms there 
a range of shattered sea-cliffs, parts of which tower for 1000 feet above the Atlantic 
breakers that beat about their base. The area extends inland to the slopes on the west 
side of Loch Sgathaig, a distance of about three and a half miles, descending in a range 
of precipices along its northern front, and reaching in its culminating summit, Orval, a 




y 

d a 

Fig. 51.— Section on north side of Orval, Rum. a, Cambrian sandstones; b, bedded basalts of Fionn Chro ; 

c, dolerite ; d, quartz-porphyry. 

height of 1868 feet above the sea. The rocks of which this triangular area consists 
resemble those of the Mull bosses. They are chiefly quartz-porphyries, becoming f elsitic 
in texture towards their contact with adjacent rocks. In some places, as was noticed by 
Macculloch on the sea-cliffs,t they have a rudely bedded structure. Thus on the north- 
west front of Orval, this structure is shown by parallel planes that dip outwards or NW. 
at 30° to 40°, and which are made still more distinct by an occasional intrusive dyke or 
sheet of basalt between their surfaces. I shall again have occasion to refer to the 
internal arrangement of the granitoid bosses, in the account of those of Skye. 

Like the gabbros already noticed, the granophyres, porphyries, and felsites of Eum 
have been intruded at the base of the volcanic series, and over much, if not all, of their 
area lie directly on the red Cambrian (Torridon) sandstone. That the bedded basalts 
once covered them is shown by the position of the three outliers of the basalt-plateau 
already noticed. But a fourth outlier still lies upon the porphyry of Orval as a cake that 
dips gently northward. It consists of a bedded, dark, finely crystalline, ophitic dolerite, 
porphyritic in places, with a rudely prismatic or columnar structure (fig. 51). It has 
undergone contact metamorphism, and tongues from the underlying rock project up 

* Quart. Jour. Geol. Soc, xxvii. (1871) p. 294. t Western Islands, vol. i. p. 487. 



160 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



into it. On the south-eastern side of the same hill, still more striking evidence is 
presented of the posteriority of the acid to the basic rocks. The porphyry shows here 
the same tendency to assume a bedded structure, the parallel " beds " again dipping 
outward or SE. at 40°. They plunge under the body of gabbro, dolerite, and other 
intrusive masses which from this point stretch eastward into the great cones of Allival 
and its neighbours. The rock at the junction is a fine microgranite with traces of micro- 
pegmatite. It is composed of a holocrystalline base of quartz and orthoclase, with 
porphyritic crystals of microcline, blebs of quartz and scattered granules of augite. The 
rocks that rest immediately next it are basalt and dolerite, into which it has sent an 
intricate network of veins (fig. 52). # It sends also long tongues down the slope into 
these rocks, some of which may be seen traversing the dolerite and gabbro veins that cut 
the basalts. The basic rocks next the porphyry have been intensely altered. They seem 
in places as if they have been shattered by some explosive force, and had then been 
invaded by the mass that rushed into all the rents thus caused. The nature of the 
contact metamorphism produced by the acid protrusions is described at p. 167. 




Fig. 52. — Junction of Quartz-Porphyry (Microgranite) and Basic Rocks, south-east side of Orval, Rum. 
a, basalts and dolerites ; b, dolerite and gabbro veins ; c, quartz-porphyry cutting a and 6. 

c. Skye. — It is in the island of Skye that the granitoid bosses attain their largest 
dimensions. They cover there a total area of about 25 square miles, and form char- 
acteristic groups of hills from 2000 to 2500 feet in height. On the south-east side, a 
group of three conspicuous cones rises from the valley of Strath (Beinn Dearg Mhor 
Beinn Dearg Bheag, and Beinn na Caillich). A solitary graceful pointed cone (Beinn na 
Cro) stands between Strathmore and Strathbeg, while to the north-west a continuous 
chain of connected cones runs from Loch Sligachan up into the heart of the Cuillin Hills. 
Their conical outline, their smooth declivities, marked with long diverging lines of screes, 
and their pale reddish or reddish-yellow hue, that deepens after a shower into glowing 
orange, mark off these hills from all the surrounding eminences, and form in especial a 
singular contrast to the black, spiry, and rugged contours of the gabbro heights to the west 
of them. 

Besides this large continuous mass, a number of minor bosses are scattered over the 
district. Of these the largest forms the ridge of Beinn an Dubhaich, south of Loch 

* In a thin slice cut from a specimen showing the junction, there is a minute vein of the porphyry penetrating the 
basalt which is much altered, while the porphyry becomes much finer in grain than at a distance from the contact. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 161 

Kilchrist. Several minor protrusions lie between that ridge and the flank of Beinn 
Dearg. Another forms the moory ground above Corry ; several occur on the side of the 
Sound of Scalpa, about Strollamus ; and one, already referred to, lies at the eastern base 
of Blath Bheinn. 

In so extensive a tract, there is room for considerable diversity of composition and 
texture among the rocks of which it consists. I have already stated that in some 
places, more particularly in the central parts of the hills, the rock assumes the character of 
a granite, being made up of a noncrystalline aggregate of quartz, orthoclase, plagioclase, 
hornblende, and biotite, without granophyric structure. It is then a hornblende-biotite- 
granite (quartz-syenite, granite-syenite of Zirkel, or amphibole-granitite of Eosenbusch). 
By the development of the micropegmatitic structure and radiated spherical concretions, it 
passes into granophyre. By the appearance of a felsitic ground-mass, it shades off into 
different varieties of quartz-porphyry (rhyolite of some authors), sometimes with distinct 
bi-pyramidal crystals of quartz.* As it is convenient to adopt some general term to 
express the whole series of varieties in the Skye area, I shall use the word granophyre 
for this purpose. 

That the large area of these rocks in Skye must have been the result of many 
separate protrusions from distinct centres of emission may be inferred, I think, not 
only from the varieties of petrographical character in the material, but also from the 
peculiar topography of the ground, and perhaps from the curious relation which seems, 
in some instances at least, to be traceable between the external features and apparent 
internal structure of the hills. It will seen from the map (Plate II.) that in the area lying 
to the east of Strath More, the granophyre is broken up into nearly detached portions by 
intervening patches of older rocks. There can be little doubt that the mass of Beinn na 
Caillich and the two Beinn Deargs is the product of a distinct orifice, if not of more 
than one. Beinn na Cro, lying between its two deep bounding glens, is another 
protrusion. The western cones stand so closely together that their screes meet at the 
bottoms of the intervening valleys. Yet each group is not improbably the result of 
emission from an independent funnel. 

But, though I believe this large area of granitoid rock to have proceeded not from one 
but from many orifices, I have only here and there obtained, from the individual hills 
themselves, indications of an internal structure suggestive of distinct and successive 
protrusions of material from the same vent of discharge. On the outer declivities of 
some of the cones, we may detect a repetition of that rudely bedded structure to which 
reference has been made as occurring in Eum. This structure is specially observable 
along the east side of Glen Sligachan. Down the northern slopes of Marsco the 
granophyre (here in part a hornblende-biotite-granite) is disposed in massive sheets 
or beds that plunge outwards from the centre of the hill at angles of 30° to 40°. On the 
southern front of the same graceful cone, as well as on the flanks of its neighbour, Ruadh 

* The best account yet published of these varieties in Skye is that by Prof. Zirkel, Zeitsch. Deutsch. Geol. Gesellsch., 
xxiii. (1871) p. 88. 



162 DR GETKIE ON THE HISTORY OF VOLCANIC ACTION 

Stac, still plainer indications of a definite arrangement of the mass of the rock in irregular 
lenticular beds may be noticed. These beds, folding over the axis of the hill, dip steeply 
down as concentric coats of rock. The external resemblance of the red conical mountains 
of Skye to the trachyte puys of Auvergne was long ago remarked by J. D. Forbes,* and 
in this internal arrangement of their materials, indefinite though it may be, there is a 
further resemblance to the onion-like coatings whieh Scrope thought he could detect in 
the interior of the Grand Sarcoui.t 

Where the contour of the cones is regular, and the declivities are not marked by 
prominent scars and ribs of rock, this monotony of feature betokens a corresponding 
uniformity of petrographical character. But where, on the other hand, the slopes are 
diversified by projecting crags and other varieties of outline, a greater range of texture 
and composition in the material of the hills is indicated. This relation is well brought 
out on the western front of Marsco, where numerous alternations of granitoid and felsitic 
textures occur. On many declivities also, which at a distance look quite smooth, but 
which are really rough with angular blocks detached from the parent mass underneath, an 
occasional basalt-dyke will be observed to rise as a prominent dark rib. A good example 
of this structure is to be seen on the south front of Beinn na Caillich. Where a group of 
dark parallel dykes runs along the sides of one of these pale cones it sometimes produces 
a curiously deceptive appearance of bedding. A good illustration may be noticed on the 
southern front of Beinn Dearg Meadhonach, north from Marsco. When I first saw that 
hillside I could not realise that the parallel bars were actually dykes until I had crossed 
the valley and climbed the slopes of the hill.| 

Occasionally round the margin of the granophyre a singular brecciated structure is to 
be seen. It is most marked on weathered faces, and may be observed on the flanks of 
Glamaig and of Marsco. But when the rock is broken open, it is less easy to detect the 
angular and subangular fragments from the surrounding matrix, which is finely crystalline 
or felsitic. 

The actual junction of the eruptive mass with the surrounding rocks through which it 
has ascended is generally a nearly vertical boundary, or the granophyre plunges at a 
steep angle under the rocks that lie against or upon it. On the north of Glamaig, for 
instance, the porphyritic and felsitic margin of the great body of eruptive rock descends 
as a steeply inclined wall, against which the red sandstones and marls at the base of the 
Secondary formations are sharply tilted. On the south side of the area, a similar steep 
face of fine-grained rock forms the edge of the granophyre of the great southern cones, 
and plunges down behind Lias limestone and shale, Lower Silurian limestone and 
quartzite, or portions of the Tertiary volcanic series. Yet there can be no doubt that, 
along many parts of the boundary-line, the eruptive mass extends underneath the surface 

* Edin. New Phil. Jour., xl. p. 78. t Geology and Extinct Volcanoes of Central France, 2d edit., p. 68. 

X The difference of contour and colour between the ordinary reddish smooth-sloped " syenite " and the black craggy 
" hypersthene rock" and "greenstone" at the Glamaig group of hills caught the eyes of Von Oyenhauskn and Von 
Dechen (Karsten's Archiv, i. p. 83). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 163 

far beyond the actual base of the cones, for projecting knobs as well as veins and dykes 
of it rise up among the surrounding rocks. This may be well seen along the northern 
foot of Beinn na Caillich. But of all the Skye bosses none exhibits its line of junction 
with the surrounding rocks so well and continuously as Beinn an Dubhaich. This isolated 
tract of eruptive material lies entirely within the area of the Lower Silurian limestone, 
and its actual contact with that rock, and with the basalt-dykes that traverse it, can be 
examined almost everywhere. The junction is usually vertical or nearly so, sometimes 
inclining outwards, sometimes inwards. It is notched and wavy, the granophyre sending 
out projecting spurs or veins, and retiring into little bays which are occupied by the 
limestone. The rock of the boss is massive and jointed, splitting up into great quad- 
rangular blocks like a granite, and weathering into rounded boulders. It is in some 
parts a hornblende-biotite-granite, its granitic composition and texture being best seen 
where the mass is broadest, south of Kilbride. Towards its margin, on the shore of 
Camas Malag, the granophyric structure appears especially in narrow ribbons or veins 
that run through the more granitic parts of the rock. 

Immediately to the south of this bay, the junction with the limestone is well displayed, 
and the eruptive rock, which is there granitic in character, sends out into the limestone 
a vein or dyke about two feet broad, of closer grain than the main body of the boss, but 
showing a distinctly granitic structure. The junction on the north side is equally well 
seen below the crofts of Torran. Here the rock of the boss, for a few yards from its 
margin, assumes a fine-grained felsitic aspect, and under the microscope presents a curious 
brecciated appearance, suggestive of its having broken up at the margin before final 
consolidation. Portions of the already crystallised granite seem to be involved in a 
microgranitic base. The rock has here truncated a number of basalt-dykes which inter- 
sect the Silurian limestone. 

On the surface of the mass of Beinn an Dubhaich, a few little patches of limestone 
occur to the south of Kilchrist Loch. Considering the nearly vertical wall which the 
granophyre presents to the adjacent rock all round its margin, we may perhaps reasonably 
infer that these outliers of limestone are remnants of a once continuous limestone sheet 
that overlay the eruptive rock, and hence that, with due allowance for considerable 
denudation, the present surface of the boss represents approximately the upper limit to 
which the granophyre ascended through the limestone. The actual facts are shown in 
fig, 53. 

All round the margin of this boss, the limestone has been converted for a variable 
distance of a few feet or many yards into a granular crystalline marble. The lighter 
portions of the limestone have become snowy white ; but some of the darker Carbonaceous 
beds retain their dark tint. The nodules of chert, abundant in many of the limestones, 
project from the weathered faces of the marble. The dolomitic portions of the series 
have likewise undergone alteration into a thoroughly crystalline-granular or saccaroid 
rock. The most thorough metamorphism is exhibited by portions of the limestone 
which are completely surrounded by and rest upon the granophyre. The largest of these 



164 



DR-GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



overlying patches was many years ago quarried for white marble above the old Manse 
of Kilchrist. I have recently shown that this limestone, instead of belonging to the 
Lias, forms a part of the Lower Silurian series, being a continuation of the fossiliferous 
limestone of western Sutherland and Ross-shire.* 

The generally vertical line of separation between the rock of Beinn an Dubhaich and 
the contiguous limestone has been taken advantage of for the segregation of mineral 
veins. On the southern boundary at Camas Malag, a greenish flinty layer, from less than 
an inch to two or three inches in width, consisting of a finely granular aggregate of 
some nearly colourless mineral, which polarises brilliantly, coats the wall of the 
granophyre, and also both sides of the vein which proceeds from that rock into the 
limestone. But the most abundant and interesting deposits are metalliferous. 
Fragments of a kind of " gossan " may be noticed all along the boundary-line of the 
boss, and among these are pieces of magnetic iron-ore and sulphides of iron and copper. 
The magnetite may be seen in place immediately to the south of Kilbride. A mass of 
this ore several feet in diameter sends strings and disseminated particles through the 




Fig. 53. — Section across the north slope of Beinn an Dubhaich. aa, Lower Silurian limestone ; 

lb, basalt dykes ; c, granophyre. 

surrounding granophyre, and is partially coated along its joints with green carbonate of 
copper. 

Relations of the Granophyre to other Members of the Volcanic Series. — It is the 
connection of the eruptive bosses of acid rocks with the other members of the volcanic 
series that is chiefly of interest for the purpose of the present memoir. From the Skye 
area, important evidence is obtainable in regard to the relation of these bosses to (1) 
earlier eruptive vents filled with agglomerate ; (2) the bedded basalts of the plateaux ; 
(3) the sheets and bosses of gabbro and dolerite ; and (4) the great system of basic dykes. 

(1) Relation to older Eruptive Vents. — The granophyre of Beinn na Caillich and the 
two Beinn Deargs has invaded on its north-eastern side the Lower Silurian limestone 
and quartzite, and has truncated the sheets of intrusive dolerite and gabbro that have 
there been injected into them. But to the south-west it rises through the great mass of 
agglomerate already described, and continues in that rock round to the entrance into 

* Quart. Jour. Geol. Soc, vol. xliv. (1888) p. 62. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 165 

Strath Beg. Judging from the respective areas of the granophyre and agglomerate, we 
may infer that the former has not risen here exactly in the centre of the old funnel, but 
rather to the north of it. It is no doubt this fortunate divergence that has spared a 
segment of the vent from obliteration. It is interesting to observe, however, that the 
granophyre has likewise risen along the outer or southern margin of the agglomerate, 
generally between that rock and the limestone, but sometimes entirely within the 
agglomerate. The distance between the nearest part of this ring of eruptive rock and 
the edge of the boss of Beinn an Dubhaich is under 400 yards, the intervening space- 
being occupied by limestone (or marble), much traversed by N.W. basalt-dykes. These 
dykes do not enter the rocks of the veDt, and are abruptly truncated by the mass of 
Beinn an Dubhaich. The structure of this locality in shown in fig. 54. Further 
westward, the group of vents, which as we have seen probably rose out of the plateau 
basalts, first served for the rise of the masses of gabbro, and the subsequent pro- 
trusion of the granophyres has destroyed or concealed any relics of it that might have 
survived. 




Fig. 54. — Section from Beinn Dearg to Beinn an Dubhaich, Skye. aa, Lower Silurian limestone; bb, volcanic agglomerate ; 
ccc, basalt-dykes older than granophyre; d 1 , granophyre of Beinn Dearg; cP, granophyre in the agglomerate neck; d 3 , 
granophyre of Beinn an Dubhaich ; e, basalt-dyke younger than granophyre. 

(2) Relation to the Bedded Basalts of the Plateaux. — On the north-west side, the 
granophyre of Glamaig and Glen Sligachan mounts directly out of the bedded basalts. 
These latter rocks, which rise into characteristic terraced slopes on the north side of Loch 
Sligachan, appear on the south side immediately to the west of Sconser, and stretch west- 
wards round the roots of Glamaig into the Coire na Sgairde. As they approach that hill 
they assume the usual dull, indurated, splintery, veined character, where they have under- 
gone contact metamorphism, and weather with a light crust. Some of them are highly 
amygdaloidal, and between their successive beds thin bands of basalt-breccia, also 
much hardened, occasionally appear. Veins of granophyre become more numerous 
as we come nearer the main mass of that rock. The actual line of junction runs 
into the Coire na Sgairde and slants up the Druim na Euaige, ascending to within a 
few feet of the top of that ridge. A dark basic rock lies on the granophyre, the latter 
being here finer grained and greenish in colour, and projecting up into the former. There 
is so much detritus along the sides and floor of Glen Sligachan that the relations of the 

VOL. XXXV. PART 2. Y 



166 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

two groups of rock cannot be well examined there. But the basalts, which present their 
ordinary characters to the north of the Inn, are observed to become more and more 
indurated, close-grained, dull, and splintery as they draw nearer to the granophyre of 
Marsco. This part of the district furnishes the clearest evidence of the posteriority of 
the great cones of Glamaig and its neighbours to the plateau-basalts which come up to 
the very base of these hills. 

Round the eastern group of cones some interesting fragments of the once continuous 
sheet of basic rocks remain, to show the same relation of the acid protrusions on that side. 
One of these lies on the granophyre of the flanks of Beinn na Caillich, a little to the west 
of the loch at the northern base of that hill. Another of larger size forms a prominent 
knob about three-quarters of a mile further west, and is prolonged into the huge dark 
excrescence of Creagan Dubha, which rises in such striking contrast to the smooth red 
declivities of the granophyre cones around it. This prominence at its eastern and 
northern parts consists of highly indurated splintery basalt in distinct beds, some of 
which are strongly amygdaloidal. The bedding is nearly vertical, but with an inclination 
inwards to the hill. Towards the south-west end a thin band of basalt-breccia makes its 
appearance between two beds of basalt. Its thickness rapidly increases southward until 
it is the only rock adhering to the granophyre. Beyond the foot of the hill, Lower 
Silurian limestone and quartzite occupy for some distance the bottom of Strath Beg, 
much invaded by masses of quartz-porphyry. At the summit of Creagan Dubha 
abundant veins run into the basic rocks from the granophyre, which, as usual, is finer 
grained towards the margin ; and there are likewise veins of quartz-porphyry which, 
though their actual connection with the main mass of granophyre cannot be seen, are no 
doubt apophyses from it. 

This outlier of altered basalt and breccia appears to me to be a fragment of the 
plateau-basalts which once overlay the Silurian rocks of Strath Beg, and were dis- 
rupted by the uprise of the granophyre. It continues to adhere to the wall of the 
eruptive mass that broke up and baked its rocks. Its breccia, passing southward into a 
coarse agglomerate, is doubtless a product of the same vent that discharged the great 
agglomerate mass above Kilbride and Kilchrist. I have already (p. 109) referred to 
what appears to be another outlier of the basalts on the south side of Beinn Dearg. 

On the northern and southern flanks of Beinn na Cro, similar evidence may be 
observed of the posteriority of the granophyre to the basic rocks. Round the northern 
base of the hill a continuous tract of basalts, dolerites, and gabbros forms the ridge 
between Strathmore and Strathbeg. There is an admirable section of the relation of the 
two groups of rock on the eastern side of the western glen. Along the lower part of 
the declivity, coarsely-crystalline gabbros, like some of those in the Cuillin Hills, are- 
succeeded by sheets of dolerite and basalt, the whole forming an ascending succession of 
beds to the summit of the ridge. The edges of these beds are obliquely truncated by the 
body of granophyre, which slants up the hill across them and sends veins into them. They 
are further traversed by basalt dykes, which here as almost everywhere abound (fig. 55). 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



167 



On the south side of Beinn na Cro, highly indurated black and grey Lias shales and 
sandstones have been tilted up steeply and indurated by the eruptive rock of the hill ; 
and at one place some 800 feet above the sea, a little patch of altered basalt, lying on 
the shale but close up against the steep declivity of granophyre, forms a conspicuous 
prominence on the otherwise featureless slope. 

I have reserved for the present section of this memoir a fuller account of the meta- 
morphism of the basalts, to which frequent allusion has been made as one of the evidences 
of the posteriority of the eruptive bosses of rock round which it occurs. The field- 
geologist observes that the basalts as they are traced towards these bosses lose their 
usual external character. They no longer weather into spheroidal blocks with a rich 
brown loam, but project in much jointed crags, and their hard rugged surface shows when 
broken a thin white crust, beneath which the rock appears black, dull, and splintery. 
They are generally veined with minute threads or strings of calcite, epidote, and quartz, 
which form a yellowish-brown network that projects above the rest of the weathered 
surface. Where they are amygdaloid al the kernels no longer decay away or drop out, 




Fig. 55. — Section at north end of Beinn na Cro, Skye. a, basalt, dolerite, andgabbro; b, granophyre of Beinn na Cro; 

ft 1 , dyke of granophyre ; cc, basalt dykes. 



leaving the empty smooth-surfaced cells, but remain as if they graduated into the 
surrounding rock by an interlacing of their crystalline constituents. They then look at 
a distance more like spots of decoloration, and even when seen close at hand would 
hardly at first betray their real nature. 

From the specimens collected by me in Skye, Mull, and Rum, I have selected two 
dozen which seemed to be fairly typical of these altered rocks, and have placed thin 
slices of them for microscopic examination in Dr Hatch's hands. His notes may be 
condensed into the following summary. One of the most frequent features in the slides 
is the tendency in the component minerals to assume granular forms. In one specimen 
from Loch Spelve, Mull, the rock, probably originally a dolerite, shows only a few 
isolated recognisable crystals of plagioclase and augite, the whole of the rest of the rock 
consisting of roundish granules embedded in a felspathic matrix. The felspar crystals 
are sometimes broken up into a mosaic, though retaining their external contours. 
Besides the granules, which are no doubt augite, a few grains of magnetite are scattered 
through the rock, aggregated here and there into little groups. In another specimen, 



168 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

taken from the junction with the granophyre in Glenmore in the same island, parts of 
the augite crystals are converted into granular aggregates associated with large grains 
and patches of magnetite. The latter mineral also assumes in some of the rocks granular 
and even globular shapes suggestive of fusion. 

The felspars, which in most of the basic rocks are usually remarkably clear and fresh, 
show marked kaolinisation in these altered masses. Minute dusky scales of kaolin are 
developed in them, sometimes also with the separation of minute grains of quartz. The 
augite shows frequent alteration to hornblende, proceeding as usual from the exterior 
inward. In some cases only an envelope of uralite appears round the augite, while in 
others only a kernel of the original mineral is left, or the whole crystal has been changed. 
In many cases the altered substance appears as minute needles, blades, and fibres of 
actinolite. Occasionally, besides the green hornblende, shred-like pieces of a strongly 
pleochroic brown hornblende make their appearance. Serpentinous and chloritic 
substances are not infrequent. Epidote is sometimes abundant. The titaniferous iron 
has commonly passed more or less completely into leucoxene. Here and there a dark 
mica may be detected. 

Some of these features remind us of those which have often been described from zones 
of contact metamorphism. They no doubt point to the long-continued action of inter- 
stitial water, probably at a considerable temperature, and to the mutual reactions of the 
solutions thus obtained upon the original component minerals of the dolerites and basalts. 

(3) Relation to the Gabbros. — That the granophyres of Skye, like those of Mull and 
Rum, invade the gabbros, has been incidentally illustrated in the foregoing part of this 
Memoir. But as the mutual relations of the two rocks in this island have been the 
subject of frequent reference in previous writings of geologists, it is desirable to adduce 
some further evidence from a region which has been regarded as the typical one for 
this feature in the geological structure of the Inner Hebrides. No geological boundary 
is more easily traced than that between the pale reddish granophyre and the dark gabbro. 
It can be followed with the eye up a whole mountain side, and can be examined so 
closely that again and again the observer can walk or climb for some distance with one 
foot on each rock. That there should ever have been any doubt about the relations 
of the two eruptive masses is possibly explicable by the very facility with which their 
junction can be observed. Their contrasts of form and colour made their boundary 
over crag and ridge so clear that geologists do not seem to have taken the trouble to 
follow it out in detail. And as the pale rock undoubtedly underlies the dark, they have 
assumed this infrapasition to mark its earlier appearance. 

I will only cite one part of the junction line. It is easily accessible, and the 
phenomena it displays may be regarded as typical for the whole. It lies in Glen 
Sligachan immediately to the south of the mouth of Harta Corry. The rounded eminence 
of Meall Dearg, which rises to the south of the two Black Lochs, belongs to the granophyre, 
while the rugged ground to the west of it lies in the gabbro. The actual contact 
between the two rocks can be followed from the side of Harta Corry over the ridge and 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 169 

down into Strath na Creitheach, whence it sweeps northward between the red cone of 
Ruadh Stac and the black rugged declivities of Garbh Beinn. On Meall Dearg the 
granophyre becomes fine-grained and even felsitic in texture, and sends into the 
contiguous gabbro abundant veins, some of which show fine flow-structure. There is no 
more singular scene in Skye than the lonely tract on the south side of this hill. The 
ground for some way is nearly level, and strewn with red shingle from the decomposing 
granophyre underneath. It reminds one of some parts of the desert " Bad lands " of 
Western America. Grim dark crags of gabbro, streaked with red veins from the 
granophyre, rise along its western border beyond which tower the black precipices of the 
Cuillins, while the flaming reddish-yellow cones of Glen Sligachan stand out against the 
northern sky. The gabbro here includes much fine-grained, sometimes amygdaloidal rock, 
belonging probably to the plateau-basalts, and sends veins through it, but the veins 
from the granophyre-mass cross these. An alteration of the basic rocks like that already 
described may be noticed here. Next the granophyre, they are dull, compact, splintery, 
shattery, and much veined, and weather with a white crust. 

(4) Relation to the Basic Dykes and Veins. — In my early paper on the Geology of 
Strath I pointed out that the " syenite " bosses of Skye cut off most of the basalt-dykes, 
but are themselves traversed by a few others.* Though I have since been able to 
confirm and extend this observation, the locality that furnished my original evidence 
affords in small compass a clearer presentation of the facts than I have elsewhere met 
with. I then referred to the sections visible at the eastern end of the boss of Beinn an 
Dubhaich ; but similar and even better ones may be cited from the whole northern 
and southern margins of that eruptive rock. On the north side an extraordinary 
number of dykes may be traced in the limestone from the shores of Loch Slapin east- 
wards. They have a general north-westerly trend, but one after another, as I have 
already remarked, they are abruptly cut off by the granophyre. The latter rock is 
exposed for nearly a mile in almost continuous section along the shore of Loch Slapin. 
Yet though I was on the outlook for dykes in it, I found only one. Immediately 
beyond the eruptive boss, however, they at once appear on either side up to the very 
edge of the granophyre, where they abruptly cease. The conclusion cannot be resisted 
that the protrusion of the acid rock took place after most of the dykes of the district 
had been formed, but before the emission of the very latest dykes which pursue a north- 
west course across the boss (fig. 54). 

Some sections on the southern margin of Beinn an Dubbaich complete the demon- 
stration that such has been the order of appearance of the rocks. Near the head of 
the Allt Leth Slighe (or Half-way Burn), where the granophyre sends a long tongue 
into the limestone, a N.W. basalt dyke is abruptly cut off by the main body of the 
boss and by the protruded vein (fig. 56). Besides this truncation, the acid rock protrudes 
strings and threads of its own substance into and across the dyke, these injected portions 
being as usual of an exceedingly fine felsitic texture. 

* Quart. Jour. Geol. Soc, xiv. p. 16. 



170 DR' GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

Similar evidence may be gathered from the area of the great granophyre cones 
further north. The profusion of basalt-dykes in the surrounding rocks stops short at the 
margin of that area. The comparatively few dykes which cross the boundary pursue a 
general N.W. course through the granophyre, and as already remarked, from their dark 
colour, greater durability and straightness of direction stand out as prominent ribs on 
the flanks of the pale cones which they traverse. 

d. St Kilda. — I have not personally visited this remote island, of which the only 
geological account we have is that by Macculloch. But through the kindness of my 
colleague, Mr John Horne, F.E.S.E., I have had a series of specimens submitted to me 
which were collected by Mr A. Ross of Inverness. These prove that in St Kilda, not 
only are the rocks of the mountainous parts of Skye and Mull repeated, but that their 
relative order of appearance is likewise the same. The olivine-gabbros and the granitoid 
and granophyric rocks are precisely those of the Inner Hebrides. One of the specimens 
shows a vein of fine granite traversing an ophitic dolerite, and another is a piece of altered 
fine dolerite or basalt, from near the junction with the acid rocks, and weathers with the 
white crust so characteristic of similar rocks in the districts above described. 




/\J- 



Fig. 56. — Section showing the Truncation of a Basalt Vein (5), in Lower Silurian Limestone (a), 
by the Granophyre (c) of Beinn na Dubhaich, Skye. 

e. Antrim. — In the volcanic region of the north of Ireland the areas of acid rocks are 
comparatively few in number, and small in size. They nowhere assume the form of 
prominent hills, and indeed would never attract attention from anything conspicuous in 
their topography. The largest of them covers a space of about 10 square miles in the 
heart of the basalt-plateau to the north-east of the town of Antrim, rises to about 1000 
feet above the sea, and forms a few featureless hills, some of which are capped with basalt. 
The best known localities in this tract are Tardree and Carnearny. The rock is chiefly a 
quartz-trachyte, but here and there pieces of pitchstone and pearlstone may be picked up, 
which, though I could not find them in place, I have no doubt form part of the main 
trachyte mass. 

Owing to the cover of soil and turf, the junction of this rock with the basalts of the 
plateau cannot be so clearly seen as in the sections of the Inner Hebrides, and hence the 
stratigraphical relations of the two groups are apt to be misunderstood. What is actually 
seen is represented in fig. 57. It has been supposed that the trachyte forms the summit 



DURING THE TERTIARY PERIOD IN" THE BRITISH ISLES. 171 

of an ancient volcanic dome that had been erupted and worn down before the outflow of 
the basalts which gradually accumulated around and over it. # Had this been the true 
history of the locality, it is inconceivable that of a rock which decays so rapidly as this 
trachyte, and strews its slopes with such abundance of detritus, not a single fragment 
should occur between the successive beds of basalt which are supposed to have surrounded 
and buried it. Though the several beds of basalt are well exposed all round, I could not 
find a trace of any trachytic fragments between them, nor has Mr Symes, who mapped 
the ground in detail for the Geological Survey, been more successful. The basalts near 
the trachyte are hard and splintery, but not so distinctly altered as round the granophyre 
in the Inner Hebrides. Were there no other evidence than that furnished by this 
Antrim locality regarding the relation of the acid and basic rocks of the Tertiary volcanic 
series of Britain, the question, I admit, could not be satisfactorily settled. But when we 
compare the Antrim sections with those of the west of Scotland, particularly with those 
of Mull (figs. 43, 46), we see their close resemblance, and can hardly hesitate to regard 
the Irish trachyte as later than the basalts around it. For my own part, I have little 
doubt that the trachytes and pitchstones are not only far younger than the plateau-basalts, 
but are even later than the granophyres.t 




Fig. 57. — Section across the southern slope of Camearny Hill, Antrim, aaa, bedded basalts; b, trachyte. 

Besides this largest boss of trachyte a number of smaller knobs of trachytic, rhyolitic, 
perlitic, and vitreous rocks appear at intervals both to the north and south of the Tar- 
dree mass, entirely surrounded by basalt. Most of these lie within the area of the lower 
group of basalts, but one of them to the south-east of Ballymena appears to cross from 
that group into the upper basalts. These scattered patches, I have no hesitation in 
believing to be intrusive bosses, sheets, or veins, which, like those of Mull and Skye, have 
been injected into the basalts long after these rocks had been built up into the plateaux. 

* For an early account of the Antrim trachytic rocks, see Berger, Trans. Geol. Soc, iii. (1816) p. 190. Professor 
Hull has described the Tardree rock in the Explanation to Sheets 21, 28, and 29, Geol. Survey of Ireland (1876), p. 17, 
and has supposed it to be older than the basalts, referring it to the Eocene period. Dupfin (quoted by Mr Kinahan) 
believed that " the trachytes occur at the centres of eruption, and were probably poured out at the end of the outburst." 
Du Noyer also (quoted by the same writer) thought them to be newer than the plateau-basalts, and to have lifted up 
masses of these rocks. Mr Kinahan himself (Geology of Ireland, p. 172) has pointed out the absence of any trachytic 
fragments between the basalts as an argument against the supposed antiquity of the acid protrusions. A full petro- 
graphical account of the Tardree rock is given by Von Lasaulx in the paper already cited, Tschermak's Min. Pet. 
Mittheil, 1878, p. 412. 

t [Since this paper was read, and as it is passing through the press, I have received from Mr A. M'Henrt, of the 
Geological Survey, some interesting information recently obtained by him at Templepatrick, co. Antrim. He has 
there found what he considers to be conclusive evidence that the trachyte is intrusive in the Lower Basalts ; but that it 
is pierced by younger basic dykes. This is precisely the structure which my experience in the Inner Hebrides would 
have led me to expect.] 



172 DR GEIKTE ON THE HISTORY OF VOLCANIC ACTION 

2. Sills or Sheets. 

Not only have the acid rocks been protruded in huge bosses, they have also been 
injected in sheets between the bedding planes of stratified rocks, between the surfaces of 
the basalt-beds, and between the bottom of the plateau-basalts or of the gabbros and the 
platform of older rock on which the volcanic series has been piled up. Every gradation of 
size may be observed, from mere partings not more than an inch or two in thickness, up 
to massive sheets, which now, owing to the removal of their original covering of rock by 
denudation, form minor groups and ranges of hills. Where the sheets are numerous, they 
are usually small in size ; where, on the other hand, they are few in number, they reach 
their greatest dimensions. 

In Mull they are profusely abundant throughout the central mountainous tract 
between Loch na Keal and Loch Spelve. If we ascend the slopes from the Sound of 
Mull, for instance, we have not gone far before some of these sheets make their appearance. 
They are usually dull granular quartz-porphyries, often only two or three feet in thick- 
ness, and interposed between the beds of basalt that form the mass of the hills. Along 
the crest of the ridge that stretches through Beinn Chreagach Mhor to Mainnir nam Fiadh 
they take a prominent place among the ledges of basalt, basalt-conglomerate, and dolerite. 
The largest sheet in Mull is probably that which has thrust itself between the base of the 
basalts and the underlying Jurassic strata and crystalline-schists on the shore of the 
Sound of Mull at Craignure. The porphyry of this sheet is referred to by Zirkel as 
only a finer-grained variety of the same quartziferous rock, with hornblende and ortho- 
clase crystals, which in Skye breaks through the Lias.* On the south coast also, at the 
base of the thick basalt series, similar porphyries have been injected into the underlying 
strata ; and under the great gabbro mass of Ben Buy similar protrusions occur. But as 
we retire from the mountainous tract into the undisturbed basalts of the plateau, these 
acid intercalations gradually disappear. 

In the islands of Eigg and Eum, excellent examples occur of the tendency which 
the sheets of porphyry or granophyre manifest to appear at or about the base of the 
bedded basalts. I have already alluded to the boss or sheet at the north end of the 
former island. A still more striking illustration occurs in Rum. All along the base of 
the great mass of gabbro, protrusions of various kinds of acid rock have taken place. 
The great mass of Orval, already described, is one of these. Below Barkeval and round 
the foot of the hills to the south-east of that eminence an interrupted band of quartz- 
porphyry may be traced, from which veins proceed into the gabbros and clolerites. 

But it is in Skye and Raasay that the intrusive sheets of the acid group of rocks 
reach their chief development. They form a band or belt which, though not continuous, 
can be traced round the east side of the main body of granophyre at a distance of from 
a mile and a half to about three miles. Beginning near the Point of Suisnish, this belt 
curves through the hilly ground for some five miles until it dies out on the slopes above 

* Zeitsch, Deutsch. Geol. Geselhch,, xxiii. p. 54. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 173 

Skulamus. It may be found again on the west side of the ridge of Beinn Suardal and 
on the moors above Corry till it reaches the shore at the Rudh' an Eireannich 
(Irishman's Point). It skirts the west side of Scarpa Island, and runs for some miles 
through Kaasay. 

Over a large part of its course, the rocks of this belt rest as a great overlying sheet 
upon the Jurassic strata, which may almost everywhere be seen dipping under them. 
From the analogy of other districts, we may, I think, infer that their position indicates 
the intrusion of these sills at the base of the plateau-basalts which have since been 
removed from almost the whole tract. Fortunately, a portion of the basalts remains in 
Raasay, and enables us to connect that island with the great plateau of Skye of which it 
once formed a part. There can be no doubt that the amygdaloidal basalt-beds of the 
Dun Caan ridge once extended westwards across the band of granophyre which now 
forms most of the surface between that ridge and the Sound of Raasay. A thin sheet of 
quartz-porphyry, interposed among the Oolitic strata, may be seen a little inland from 
the top of the great eastern cliff and below the position of the bedded basalts. 

The great sheet, or rather series of sheets, which stretches north-eastwards from 
Suisnish consists of a rock which for the most part may readily be distinguished in the 
field from the granitoid material of the bosses. It appears to the naked eye to be a 
rather close-grained or finely crystalline-granular quartz-porphyry, with scattered blebs or 
bi-pyramidal crystals of quartz and crystals of orthoclase. At the contact with adjacent 
rocks, the texture becomes more felsitic, sometimes distinctly spherulitic (W. side of 
Carn Nathragh, next Lias shale). Under the microscope the rock is seen to be a fine- 
grained granophyric porphyry or porphyritic granophyre. It caps Carn Dearg (636 feet) 
above Suisnish, where it covers a space of nearly a square mile, and reaches at its eastern 
extremity (Beinn Bhuidhe), a height of 908 feet above the sea (fig. 14). This rock rests 
upon a sill of dolerite, and is apparently split up by it. But, as I have already stated, 
the basic rock is probably the older of the two, and the granophyre seems to have wedged 
itself between two earlier doleritic sheets. To the north-west of Carn Dearg, above 
the northern end of the crofts of Suisnish, the same sill, or one occupying a similar 
position, crops out between masses of granophyre, and is intersected by narrow veins from 
that rock. 

Though severed by denudation, the large sheets of granophyre to the east of Beinn 
Bhuidhe are no doubt continuations of the Carn Dearg mass, or at least occupy a similar 
position. That they are completely unconformable to the Jurassic rock is shown by the 
fact, that while at Suisnish they lie on sandstones which must be fully 1000 feet above the 
bottom of the Lias, only two miles to the east they are found resting on the very basement 
limestones within a few yards from the underlying quartzite and Cambrian sandstone. 
I do not think that this transgression can be accounted for by intrusion obliquely across 
the stratification. I regard it as arising from the eruptive rock having forced its way 
between the bottom of the now vanished basalt-plateau and the denuded surface of 
Jurassic rocks, over which the basalts were poured. The platform underneath these 

VOL. XXXV. PAKT 2. Z 



174 



DRGEIKIE ON THE HISTORY OF VOLCANIC ACTION 



gianophyre sills thus represents, in my opinion, the terrestrial surface before the beginning 
of the volcanic period. 

But there is abundant proof that though the intruded granophyre sills followed 
generally this plane of separation, they did not rigidly adhere to it, but burrowed, as it 
were, along lower horizons. Thus on the south-east front of Beinn a' Chairn, which forms 
so fine an escarpment above the valley of Heast, the base of the granophyre, after creeping 
upward across successive beds of limestone, sends out a narrow tongue into these strata, 




FlG. 58. — Section across tlie Granophyre Sills at Loch a' Mhullaich, above Skulamus, Skye. a, Jurassic sandstones and 
shales; b, Jurassic dark brown sandy shales; c, sills of basalt, some bands highly cellular; c 1 , basalt-sill with veins of 
felsite rising into it from the granophyre below; dd, intrusive sheets or sills of granophyre. 

and. continues its course a little higher up in the Lias. The same rock, after spreading 
out into the broad flat tableland of Beinn a' Chairn (983 feet), rapidly contracts north- 
eastwards into a narrow strip which forms the crest of the ridge, and at once suggests a 
much weathered lava-stream. The resemblance to a coulee is heightened by the curious 
thinning off of the rocks where the two streams emerge from the Heast lochs ; it looks as if 
the igneous mass were a mere superficial ridge which had been cut down by erosion, so as 
to expose the shales beneath it. But that the granophyre is really a sill becomes abun- 



Manse 



Tur Ruagh 



Millstream 




Fig. 59. — Section to show the connection of a Sill of Granophyre with its funnel of supply, Raasay. aa, Jurassic 

sandstones; b, granophyre. 



dantly clear at its eastern end, where we find that it consists of two separate sheets with 
intervening Liassic shales. The structure of this interesting locality is shown in fig. 58. 
In this instance also, there is evidence that the acid sills are younger than the basic, for 
the upper sheet of granophyre sends up into the overlying dark basaltic rock narrow 
vertical felsitic veins, a quarter of an inch to an inch in width, which being more 
durable, stand out above the decomposable surface of the containing rock, and show 
their quartz-blebs and felspar crystals on the weathered surface. 

It is not easy to determine where lay the vent or vents from which these granophyre 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 175 

sills in Skye proceeded. Possibly they may be concealed underneath some of the larger 
areas of the rock, such as those of Cam Dearg or Beinn a' Chairn. In Raasay, however, 
it is possible to connect the sheets with the funnels through which they ascended. This 
is well seen near the Manse, where the accompanying section may be observed (fig. 59). 
Owing to great denudation, the massive sheet of granophyre has been cut into isolated 
outliers which cap the low hills, and the rock may be seen descending through the 
Jurassic sandstones, which in places are much indurated. It is observable that the 
amount of contact metamorphism induced by the granophyre sills upon the rocks between 
which they have been injected is comparatively trifling. It is for the most part a mere 
induration, sometimes accompanied with distortion and fracture. 

3. Veins and Dykes. 

Besides bosses and sills, the acid rocks of the Inner Hebrides take the form of veins 
and dykes which have invaded the other members of the volcanic series. Some of these 
have already been referred to ; but a more particular description of the venous develop- 
ment of the acid rocks as a whole is now required. 

Considered as a petrographical group, these veins and dykes are marked by the 
following characters. At the one extreme we have thoroughly vitreous rocks in the 
pitchstones. Among these, however, various degrees of devitrification appear, leading us 
to the completely devitrified felsites, which occur almost entirely as veins or dykes, 
Occasionally the microgranitic structure makes its appearance. More frequently, how- 
ever, the veins and dykes consist of what macroscopically are quartz-porphyries, and 
which under the microscope can generally be resolved into granophyric porphyries or true 
granophyres. In a few instances, the veins proceeding from the granitic bosses show a 
granitic structure. 

In their mode of occurrence, the smaller protrusions of acid rocks differ considerably 
from the ordinary type of the dykes and veins of the basic group. They comparatively 
seldom form true dykes. Most frequently they occur as irregular veins, which vary much 
within a short space in thickness and direction. They never exhibit the persistent trend 
and parallelism of opposite walls, so distinctive of the basic dykes. The phenomena 
attending their eruption must have been correspondingly different. Their advent -was 
not preceded by the rending of the terrestrial crust into long parallel fissures. On the 
contrary, they seem to have been forced between the irregular rents, joints, and bedding- 
planes of the rocks, so that they often pursue a singularly sinuous course. 

Round the margin of the larger granophyre bosses, veins have sometimes been given 
off in great numbers, as has been stated above. But, for considerable distances, not a 
single vein or dyke may appear. Along the well-exposed boundary of Beinn-an- 
Dubhaich, for example, though the edge of the granophyre is remarkably notched, there 
are hardly any protrusions that deserve the name of veins. In the central mountainous 
tract of Mull, veins of various porphyries and felsitic rocks are extraordinarily abundant. 



176 



DR' GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



They appear not so much at the actual margins of the bosses (though they occur there, 
as has already been described), as in that tract of altered basalt, with intrusive sheets and 
dykes of basalt, dolerite, and gabbro, which lies within the great ring of heights between 
Loch-na-Keal and Loch Spelve. In some areas the amount of injected material appears 
to equal the mass of basic rock into which it has been thrust. Pale grey and yellowish 
porphyries and granophyres, varying from thick dykes down to the merest threads, 
ramify in an intricate network through the dark rocks of the hills, as shown in the 
accompanying illustration (fig. 60), which represents a portion of the hill-side between 
Beinn Fhada and the Clachaig River. Such a profusion of veins probably indicates the 
existence here of some large mass of granophyre, or of granite at no great depth beneath 
the surface. 

There are two horizons on which, as I have already had occasion to point out, 
protrusions of acid materials have been specially abundant. One of these is the base of 




Fig. 60. — Section of Intruded Veins of various Acid Roiks (bb), in Basalt, Dolerite, &c. (aa), above River Clachaig, Mull. 



the bedded basalts of the plateau ; the other is the bottom of the thick sheets of gabbro. 
Dykes and veins of granophyre, quartz-porphyry, felsite, and other allied rocks are 
sometimes crowded together along these two horizons, though they may be infrequent 
above or below them. But examples also occur of solitary veins in the midst of the 
unaltered plateau-basalts, at some distance from the nearest visible body of acid eruptive 
rock. Some of the most remarkable instances of this kind are to be seen among the 
basalts that form the terraced slopes on the north side of Loch Sligachan. Several thick 
dykes of granophyre run up the declivity, cutting across hundreds of feet of the nearly 
level basalt beds. Some of them can be seen on the shore passing under the sea. They 
trend in a S.S.E. direction towards Glamaig, and they are not improbably apophyses 
from that huge boss. Another example may be cited from the basalt-outlier of Strath- 
aird, where two veins of felsite, one of them a pale flinty rock showing flow-structure 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



177 



parallel to the walls, may be seen on the west front of Ben Meabost. In this case, the 
veins are three miles and a half from the granophyre mass of Strath-na-Creitheach to the 
north, four miles from that of Beinn-an-Dubhaich to the north-east, and nearly three 
miles from that of Coire Uaigneich at the foot of Blath Bheinn. 

A special place must be reserved for the pitchstone-veins. Ever since the early 
explorations of Jameson and Macculloch, the west of Scotland has been noted as one 
of the chief European districts for these vitreous rocks. From Skye to Arran, and 
thence to Antrim, many localities have furnished examples of them, but always within 
the limits of the Tertiary volcanic region. That all of the pitchstones are of Tertiary 
age cannot, of course, be proved, for some of them are found traversing only Palaeozoic 
rocks, and of these all that can be absolutely affirmed is that they must be younger than 
the lower part of the Carboniferous system. But, as most of them are unquestionably 
parts of the Tertiary volcanic series, they are probably all referable to that series. Not 
only so, but there is, I think, good reason to place them among its very youngest 
members. It is a significant fact that they almost always occur either in or close to 
granophyre bosses, the comparatively late origin of which has now been proved. The 
first pitchstone observed in Skye was found by Jameson on the flanks of the great 
granophyre cone of Glamaig. Another rises on the side of the porphyry mass of Glas 
Bheinn Bheag, in Strath Beg. A third occurs at the foot of Beinn-na-Caillich. In Bum, 
I found a pitchstone vein traversing the western slopes of the wide granophyre boss of 
Orval. In Eigg, the well-known veins of this rock inter- 
sect the plateau-basalts, but in their near neighbourhood 
lie the masses of quartz-porphyry already alluded to. 
In Ardnamurchan also, the pitchstone has been injected 
into the plateau-basalts, but there are many small veins 
of close-grained felsitic or rhyolitic rocks in the vicinity. 
In Antrim, pitchstone occurs in the midst of the trachyte 
of Tardree. The only marked exceptions to the general 
rule, with which I am acquainted, are those of the island 
of Arran. Most of the pitchstone-veins in that district 
traverse the red sandstones which lie at the base of the 
Carboniferous system, or belong to the Old Bed Sand- 
stone. But none of them are far removed from the great 
granite boss of the northern half of the island, while 
large masses of quartz-porphyry, which strikingly resemble 

some of those of Skye and Mull, lie still nearer to them. It is also worthy of notice 
that pitchstone-veins rise through the granite boss itself, the probably Tertiary date of 
which has been already referred to. 

This common association of pitchstone-veins with the Tertiary eruptive bosses of acid 
rocks can hardly be a mere accidental coincidence. It seems to me to prove a renewed 
extravasation of acid material, now in vitreous form, from the same vents that 




Fig. 61. — Pitchstone Vein traversing the 
Bedded Basalts, Rudh an Tangairt, 



178 DR'GEIKIE ON THE HISTORY OF VOLCANIC ACTION 

had supplied the granitoid, granophyric, porphyritic, and felsitic varieties of earlier 
protrusions. We must remember that the pitchstone- veins are not mere local glassy parts 
of the larger bodies of granophyre or felsite in or near which they lie. Their margins are 
sharply defined ; they are indeed in all respects as manifestly intruded, and therefore 
later masses, as are the basalt-dykes. Their occurrence, therefore, within the granophyre 
bosses proves them to be younger than the youngest of the large erupted masses of the 
Tertiary volcanic series. Whether they are also later than the latest basalt-dykes cannot 
yet be decided, for I have never succeeded in finding an example of the intersection of 
these two groups of veins and dykes. But, with this possible exception, the pitchstones 
are the most recent of all the eruptive rocks of Britain. This fact acquires additional 
interest when taken in connection with the history of the Scuir of Eigg, to be imme- 
diately referred to. 

As a rule, the intrusive pitchstones occur as veins which cannot be traced far, and 
which vary from a few yards to less than an inch in width. They generally show con- 
siderable irregularity in breadth and direction, sometimes sending out strings into the 
surrounding rock (fig. 61). The outer portions are not infrequently more glassy and 
obsidian-like than the interior. Occasionally the vitreous character disappears by 
devitrification, and the rock assumes the texture of a compact felsite or of a spherulite- 
rock.* 

4. Superficial Lava Streams. 

The question whether any of the acid volcanic rocks were actually emitted at the 
surface, fortunately does not rest in the uncertainty in which we are compelled to leave 
the same question when asked of the bosses of gabbro, but admits of a positive answer. 
One solitary example remains of a true superficial stream of acid lava — that of the Scuir 
of Eigg. But when we consider the form of the granophyre cones, as already described, 
the indication of an internal structure in some of them, corresponding more or less with 
their external form, and the occasional presence of brecciated portions along their 
maroins, it is difficult to believe that no connection was established between these cones 
and the outer air. Although no " lava," using that word in Von Bugh's comprehensive 
sense of anything that flows from a volcanic orifice, may have spread outwards from the 
necks of granophyre, the molten material may have been protruded to the daylight in 
some such form as the domite puys of Auvergne. A comparatively small amount of 
denudation would suffice to efface any evidence that the igneous rock had ever reached 
the surface. But, in actual fact, the denudation has been enormous. Not a single 
vestige now remains of a superficial discharge from any one of the numerous granophyre 
cones of Skye. 

The solitary remnant of an acid lava-stream, forming the conspicuous Scuir of Eigg, 
has already been fully described by me, and for its structure and history I must refer to 
a former paper.t contenting myself here with a brief summary, and with a statement of 

* For an account of the pitchstone veins of Eigg, see Quart. Jour. Geol. Soc, xxvii. p. 299. 
t Qucvrt. Jour. Geol. Soc, xxvii. (1871) p. 303. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



179 



new facts and inferences, obtained from a recent re-examination of the locality. The 
o-eneral form of the ridge of the Scuir will be understood from the accompanying map of 
the island of Eigg (fig. 62). The length of the ridge is two miles and a quarter, its 
Greatest breadth 1520 feet, its extreme height 1289 feet. It consists of successive sheets 
of columnar porphyritic pitchstone, and of a dull grey de vitrified felsitic rock, the whole 




Fig. 62.— Geological Map of the Island of Eigg. P, Pitchstone of Scuir ; R, old river gravel under pitchstone ; pp, small veins 
of Pitchstone; bb, dykes, veins and sheets of intrusive basalt; the short black lines running N. W. and S.E. are basalt dykes ; 
ff, granophyre sills; D, bedded basalts with occasional tuffs; F, sheet of the " pale group " of Mull; 1, 2, 3, 4, clays, shales, 
sandstones, limestones, &c. (Jurassic) ; xx, Loch Beinn Tighe ; x, Loch a Bhealaich. :»— >- General dip of the rocks. 



having a united thickness of several hundred feet. Examined in thin sections under the 
microscope, the vitreous beds present a pale brown glass, with abundant depolarising 
microlites, large porphyritic crystals of sanidine, sometimes plagioclase, and smaller 
crystals of augite and magnetite. Some of these beds have only a feebly resinous lustre, 
and resemble in some respects andesites. In one of the slides the porphyritic felspars 



180 



DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



are chiefly plagioclase. The dull grey felsitic bands show under the microscope a more 
thoroughly devitrified ground-mass, with the minutest depolarising microlites, large 
porphyritic crystals of plagioclase and sanidine, grains of augite, and sometimes 
exceedingly abundant particles of magnetite. 

That the rocks of the Scuir of Eigg are the products of several eruptions is manifest 
from their arrangement in distinct beds, and from their variation in petrographical 
character, and that they were poured into the channel of a stream which had been 
eroded out of the surface of the plateau-basalts, is proved by the survival of the shingle 
and drift wood of that channel below the bottom of the pitchstone. The general relations 
of the rocks are impressively presented on the west side of the island, where the rock of 
the Scuir is abruptly cut off by the face of the sea-precipice, which is some 500 feet high 
(fig. 63). 




Fig. 63. — Natural Section of the Sea-cliff at the south-west end of the ridge of the Scuir of Eigg. a, Bedded 
basalts of the plateau; b, basic dykes; c, gravel of old river-bed; p, Pitchstone of the Scuir. 



At both ends of the pitchstone ridge, we learn that the dykes of fine-grained basalt 
which traverse the bedded basalts, are older than the ancient Tertiary river-bed of the 
Scuir, for the river has not only eroded the bedded basalts but has cut down into the dykes. 
There is thus evidence of enormous denudation of the surface of the basalt-plateau 
before the final volcanic outbursts, and of the comparatively late date of the pitchstone. 

The sinuous ridge of the Scuir still marks the winding course of the stream whose 
channel the pitchstone effectually sealed up and preserved. Several minor spurs, which 
project from the eastern side of the main ridge, show the positions of small tributary 
rivulets that entered the principal channel from the slopes of the basaltic tableland. 
One of these, on the south-east side of Corven, must have been a gully in the basalt with 
a rapid or waterfall. The pitchstone has flowed into it, and some of the rounded pebbles 
that lay in the channel of this vanished brook may still be gathered where the degradation 
of the pitchstone has once more exposed them to the light. 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 181 

In trying to reconstruct the topography of the ground, at the time when the streams 
of pitchstone flowed, there are several little pieces of evidence which help us. Among the 
water-worn blocks of the buried river-bed, which are wrapped up in a gravel of basalt 
debris, there occur fragments of the volcanic rocks of the plateau, also of red (Cambrian) 
sandstone, quartzite, clay-slate, and white (Jurassic) sandstone. All these rocks are 
found in place at higher elevations to the north, but in no other direction. There is there- 
fore good reason to suppose that the river drained some wooded region lying to the north 
of the present island of Eigg, of which the red sandstone mountains of Ross-shire, the 
white sandstone cliffs of Skye and Eaasay, and the quartzite and slate uplands of western 
Inverness-shire are surviving fragments. That the stream, in that portion of its channel 
preserved under the Scuir, flowed from east to west, may be inferred from the angle at 
which the tributaries meet the main stream, and also from the fact that the old river-bed 
at the east end of the Scuir is considerably higher than at the west end. 

The direction of the flow of the stream may afford some indication of that of the 
pitchstone currents. There can be little doubt, I think, that the lava flowed down the 
river-valley. Its successive streams are still inclined from east to west. The vent of 
eruption, therefore, ought to be looked for, not towards the west, but towards the 
east. Nowhere within the Tertiary volcanic region is there any boss of pitchstone or any 
mass the shape or size of which is suggestive of an actual vent of discharge to the 
surface. In the island of Eigg no boss of any kind exists, save those of granophyric 
porphyry already referred to. But none of these affords any satisfactory links of 
connection with the rock of the Scuir. More probably the vent lay somewhere to the 
east on ground now overflowed by the sea. The pitchstone veins of Eigg may represent 
some of the subterranean extrusions from the same volcanic pipe, and, if so, its site could 
not be far off. But no other relic of its activity now remains. The lofty picturesque 
ridge of the Scuir, now so prominent an object in the West Highlands, once occupied 
the bottom of a valley worn out of the basaltic tableland. Prolonged and stupendous 
denudation has destroyed the connection with its source, has cut down its ends into 
beetling precipices, has reduced the former surrounding hills into gentle slopes and 
undulating lowland, and has turned the bottom of the ancient valley into a long, narrow, 
and high crest. In this worn fragment we see the only evidence which now remains, 
that towards the close of the protracted volcanic history of the Tertiary period, streams 
of acid lavas flowed out over the wasted surface of the basalt-plateaux. 

V. SUMMARY. 

In this final section of the paper, I shall briefly sketch what seem to me to have been 
the leading features in the history of Tertiary volcanic action in the British Islands. 

1. The region within which this activity manifested itself, during Tertiary time in 
Britain, cannot be very strictly defined, but if it is restricted to those parts of the country 
where igneous rocks, probably of that age, now appear at the surface, we find that it 

VOL. XXXV. PART 2. 2 A 



182 DR GEIKTE ON THE HISTORY OF VOLCANIC ACTION 

includes the north of England and of Ireland, the southern half and the west coast of 
Scotland — a total area of more than 40,000 square miles. Over that extensive region 
volcanic phenomena were displayed during an enormously protracted interval of 
geological time. The earliest beginnings of disturbance may possibly go back into the 
Eocene period, and the final manifestations may not have ceased until the Miocene, or 
even perhaps later. So protracted was the duration of the eruptions, that there was 
room for enormous topographical changes from denudation, and also for considerable 
variation in the fauna and flora, alike of land and sea. 

2. Owing to some cause which has not yet in this relation been investigated, but 
which is probably referable to secular terrestrial contraction, the volcanic region under- 
went elevation, while, at the same time, a vast subterranean lake or sea of molten rock 
appeared underneath it. Enormous horizontal tension thus arose, and at last the 
stretched terrestrial crust gave way. A system of approximately parallel fissures opened 
in it, having a general direction towards N.W. The rapid and simultaneous production of 
such a gigantic series of rents must have given rise to earthquakes of enormous magnitude 
and destructive force. The great majority of the fractures, doubtless, did not reach to 
the surface of the ground, though probably not a few did so. Such was the potency of 
this development of terrestrial energy, that the fissures ran through the most varied 
kinds of rocks and the most complicated geological structures, crossing even earlier lines 
of powerful dislocation, and yet retaining their direction and parallelism for sometimes 
50 or 100 miles. 

3. No sooner were the fissures formed than the molten lava underneath was forced 
upward into them for many hundreds or even thousands of feet above the surface of the 
subterranean lava-sea. Solidifying between the fissure walls, it formed the crowd of basic 
dykes that stands out as the most widespread and distinctive feature of the volcanic region. 

4. Where the fissures reached the surface or near to it, the molten rock would seek 
relief by egress in streams of lava. This probably occurred in many places from which 
subsequent denudation has removed all vestige of superficial volcanic manifestations. 
But, in the great range of basalt-plateaux, from Antrim through the chain of the Inner 
Hebrides, there are still left abundant remains of the surface outflows. After the con- 
vulsions ceased which produced the dykes, the communication that had been established 
between the reservoir of molten rock underneath and the upper air would be maintained, 
and repeated eruptions might take place either from the original vents or from others 
afterwards opened by the volcanic energy. 

5. For a prolonged geological period, various basic lavas (basalts, dolerites, &c.) 
continued to flow out from innumerable vents until they had filled up the hollows of the 
great valley, which then stretched from the south of Antrim northwards between the 
west coast of Scotland and the chain of the Outer Hebrides. In some places, the 
accumulated pile of such ejections even now exceeds three thousand feet, and yet we 
cannot tell how much material has been bared away from its top by denudation. The 
surface over which the lava flowed seems to have been mainly terrestrial. Here and there, 



DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 183 

between the successive sheets of basalt, the leaves, stems, and fruit of land-plants, some- 
times in most perfect preservation, may be observed, together with the remains of 
insects. It is remarkable that the volcanic discharges consisted mostly of lava. 
Fragmentary materials were comparatively insignificant in amount, and local in origin, 
though layers of fine tuff and basalt- breccias occur in all the plateaux. Neither these 
materials nor the lavas thicken towards any centres that might be taken to mark 
volcanoes of the type of Vesuvius or Etna. On the contrary, the persistent flatness and 
uniformity of the volcanic series, and the thinning out of the separate beds in different 
directions, point to the existence of many minor vents from which the discharges took 
place. The positions of not a few of these vents can still be ascertained. They are now 
filled sometimes with dolerite, sometimes with coarse agglomerate. As the pile of erupted 
volcanic materials of the plateaux gradually thickened, and the subterranean energy grew 
feebler, the ascending lava, instead of rising to the surface, was forced between the layers 
of sedimentary strata underneath or between these and the overlying basalts, so as to 
form intrusive sheets or sills. 

6. When the great plateaux of basalt had been built up to a thickness of several 
thousand feet, another remarkable episode in the volcanic history occurred. This con- 
sisted in the uprise at certain points of coarsely crystalline basic rocks, which ultimately 
solidified as dolerites, gabbros, troctolites, picrites, &c. There is reason to believe that the 
points of extravasation of these materials were mainly determined by the positions of the 
larger or more closely clustered vents of the plateau-period, where lines of weakness 
consequently existed in the terrestrial crust. Rising as huge bosses through such weak 
places, the gabbros and associated rocks raised up the overlying bedded basalts, and forced 
themselves between them, forming thus a fringe of finer-grained intrusive sills and veins 
around the central amorphous cores of more coarsely crystalline material. Whether, in 
any of these vast domes of upheaval, the summit was disrupted, so as to allow the basic 
intrusion to flow out as lava at the surface, cannot now be told, owing to enormous 
subsequent denudation. 

7. The next chapter in the chronicle shows us that probably long after the eruption 
of the gabbros, when possibly all outward symptom of volcanic action had ceased, a 
renewed outbreak of subterranean activity gave rise to the protrusion of another and 
wholly different class of materials. This time the rocks were of a markedly acid type. 
They included varieties that range from dark flinty felsites through porphyries and 
granophyres into compounds which cannot be classed under any other name than granite. 
These masses likewise availed themselves of older vents in the plateaux, and broke through 
them. They now form huge conical hills, which, in their outer aspect, and even to some 
extent in their inner structure, recall the trachytic puys of Auvergne. But the grano- 
phyres not only ascended through the basalt-plateaux and the gabbro-bosses ; they sent 
into these rocks a network of veins, and pushed their way in huge sheets or sills between 
the strata below. Around the bosses of gabbro and granophyre, the bedded basalts 
have undergone considerable contact-metamorphism. 



184 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION. 

8. The gabbro and granophyre bosses of the Inner Hebrides demonstrate with singular 
force how unreliable petrographical characters are as a test of the relative age of rocks. 
No one looking at hand-specimens of these rocks, or even studying them in the field, 
would at first suspect them to be of Tertiary date. They precisely resemble rocks of 
similar kinds in Palaeozoic and even Archaean formations. Yet, of their late appearance 
in geological time, there cannot be any possibility of doubt. 

9. After the uprise of the granophyre, and the injection of the network of felsitic 
veins, there came once more a period of terrestrial convulsion like that of the earliest 
basic dykes, but of less intensity. Again, the crust of the earth over the volcanic region 
was pushed upward and rent open by another system of parallel fissures, directed in a 
general N.N.W. line. Again, from a sea of basic lava underneath, molten rock was forced 
upwards into the rents, and thus another system of basic dykes was formed. These dykes 
are found crossing those of earlier date, and rising through the other volcanic rocks. They 
traverse the plateau-basalts from bottom to top ; they climb to the summits of the gabbro 
mountains, and they even pursue their undeviating course over the huge domes of 
granophyre. No proof has yet been found that from any of these dykes there was a 
superficial outflow of lava. But so great has been the subsequent denudation of the 
areas, that such outflows might quite well have taken place, and have subsequently been 
destroyed. 

10. Whether these basic dykes were the last manifestation of volcanic energy in our 
region cannot yet be decidedly affirmed. But, so far as the evidence at present goes, 
they are possibly older than another series of veins and dykes, consisting chiefly of 
pitchstone, which are found at many points from Antrim to the far end of the Inner 
Hebrides. These vitreous protrusions traverse every other member of the volcanic series, 
and do not appear to be themselves cut by any. At one locality, the Scuir of Eigg, 
they reached the surface, and flowed out in streams of molten rock over the basalt- 
plateau, which had now been deeply trenched into valleys and ravines by running water. 
The singularly durable pitchstone, flowing into a river-bed, has thus preserved an 
impressive memorial of the vanished topography of Tertiary time, and of the enormous 
duration of the Tertiary volcanic period in the geological history of the British Isles. 



Trans. Kay Soc-SAm" 



Vo i xryy ; plate I._ 
GEOLOGICAL SKETCH-MAP 

TERTIARY VOLCANIC AREAS 

OF THE 

By Archibald Geikie FRS. 
I GrancphyrerrachytePitctistonefc C—J Bedded Basalts ic wrth tuffs Ac 
I Gabhro, Dolerrte (intrusive) K2S Basic Dykes 




Trans .Roy. SocEcJin 1, 



VoI.yXXV, Plate H 




MEAN SCOTTISH METEOROLOGY 

FOR THE LAST THIRTY-TWO YEARS, 



DISCUSSED FOR ANNUAL CYCLES, AS WELL AS SUPER-ANNUAL CURVES; 
ON THE BASIS OF THE OBSERVATIONS OF THE SCOTTISH 
METEOROLOGICAL SOCIETY; AS FURNISHED TO, AND PUBLISHED 
BY, THE REGISTRAR - GENERAL OF BIRTHS, DEATHS, &c, IN 
SCOTLAND; AFTER BEING COMPUTED FOR THAT OFFICER AT 
THE ROYAL OBSERVATORY, EDINBURGH. 



IN THREE PARTS. 
By 0. PIAZZI SMYTH, 

LATE ASTRONOMER-ROYAL FOR SCOTLAND AND F.R.S.E., F.R.A.S., &c. 



This paper has been passed through the Press under the careful revision of Mr Thomas Heath, first 
Assistant Astronomer, and in full charge of the Koyal Observatory, Edinburgh, since Mr 
C. Piazzi Smyth's retirement on August 15, 1888. 

March 1888. 



VOL. XXXV. PART 3. 2 B 



( 186 ) 



CONTENTS. 



Table 



I. 

II. 

Ill 

IV. 

v. 

VI. 

VII. 

VIII. 

IX. 

x. 

XI. 
XII. 

XIII. 

XIV. 
XV. 

XVI. 
, XVII. 
, XVIII. 

XIX. 
XX. 

XXI. 
, XXII. 
, XXIII. 
, XXIV. 
, XXV. 
, XXVI. 
, XXVIa. 
, XXVII. 
, XXVIII. 
, XXIX. 
, XXX. 
, XXXI. 



MEAN SCOTTISH METEOKOLOGY. 

Part I.— LIST OF TABLES. 

Barometric Pressure (reduced to 32° and to the Sea-Level), 

Mean Barometric Bange, . 

Mean Temperature, . 

Mean Daily Range of Temperature, 

Mean of Black Bulb in the Sun, 

Mean of Black Bulb during Night, 

Humidity, .... 

Number of Days on which Bain Fell, 

Depth of Bain in Inches, . 

Mean Force of the Wind ; lbs. Avoir, on Sq. Foot, 

Winds— Northern Quarter, \ N.W., N., and \ N.E., 

Winds — Eastern Quarter, \ N.E., E., and \ S.E., 

Winds— Southern Quarter, \ S.E., S., and"| S.W., 

Winds— Western Quarter, \ S.W., W., and \ N.W., 

Mean Number of Hours of Sunshine, 

Mean Amount of Cloud, . 

Lightning — Mean Number of Days, 

Lightning — Number of Stations, 

Aurora — Mean Number of Days, 

Aurora — Number of Stations, 

Mean Maxima of Shade Temperature, 

Mean Minima of Shade Temperature, 

Accumulated Rainfall, 

Useful Plant-Growth Temperature, 

Progressive Accumulations of each kind of Useful Plant-Growth Temperature, 

Final Accumulations of Useful Plant-Growth Temperature, 

Black-Bulb Thermometers, Maxima and Minima Extremes, 

" Frost," in Depressions below the Freezing Point, 

" Fire," in Elevations above the Freezing Point, . 

Wind Force per Month, ...... 

Wind Force, Accumulated Quantities, 

Monthly Elements of all Scottish Meteorology, reduced to one Central 
Geographical Point, viz.: Latitude = 56° 30' N.; Longitude = 3° 40' W. 
and Height = 256 Feet (such point being further Distant from the 
General Sea-Coast, on the East, 40 Miles ; on the West, 90 ; on the 
North, 120; and on the South, 120 Miles); — and for the Mean of the 
Years 1856 to 1887 inclusive, 



PAGE 

188 
190 
192 
194 
196 
198 
200 
201 
202 
204 
206 
207 
208 
209 
210 
211 
212 
213 
214 
215 
216 
218 
220 
222 
224 
226 
228 
256 
258 
260 
262 



264 



Part II.— LIST OF PLATES. 

Plate 1, represents Table I., or Barometric Pressure ; and Table II., or Monthly Range of 
Barometric Pressure. 
„ 2, represents Composite Table I., viz., Mean of Barometric Pressure and Barometric Monthly 
Range x 3. 



CONTENTS. 



187 



Plate 3, represents Table III., or Mean Temperature in Shade ; and Table IV., or Daily Range 

of Shade Temperature. 
„ 4, represents Table V., or Black Bulb by Day; and Table VI. , or Black Bulb by Night. 
,, 5, represents Composite Table II., or Mean Shade Temperature + Mean Maxima of 

Shade Temp., +Mean of Black Bulb by Day. 
„ 6, represents Table VII., or Humidity ; and Table VII'., or Elastic Force of Vapour, due to 

both Humidity and Shade Temperature. 
,, 7, represents Table VIIL, or Days of Rainfall; and Table IX., or Annual Depth of Rainfall. 
„ 8, represents Table X., or Strength of Wind. 

Table XL, or Days of North Wind. 
Table XII, or Days of East Wind. 
Table XIII., or Days of South Wind ; and 
Table XIV., or Days of West Wind. 
„ 9, represents Table XV., or Hours of Sunshine ; and Table XVI., or Percentage of Cloud. 
,, 10, represents Table XVIII., or Occurrences of Lightning ; and Table XX., or Occurrences 

of Aurora. 
„ 11, represents Composite Table III., or Sum of Lightning and Aurora occurrences, and 

Composite Table IV, or Sum of Lightning taken two years beforehand, and Aurora in 

its own year. 
,, 12, represents Composite Table IV, or Lightning two years beforehand + three times 

the occurrences of Aurora in its own years. 
„ 13, represents Table XXL, or Mean Maxima of Shade Temperature ; and Table XXII., or 

Mean Minima of Shade Temperature. 
,, 14, represents Table XXVIL, or "Frost," in Depressions below the Freezing Point; and 

Table XXVIIL, or " Fire," in Elevations above the Freezing Point. 



Part III.— EXPLANATIONS OF THIRTY-ONE CHRONOLOGICAL TABLES. 



1. Historic Origin of the Data, ..... 

2. Of the Old Tables newly continued to the Present Time, 

3. Newly prepared Tables for New Derivations from the Old Observational Meteorology, 

4. Frost and Fire, 

5. Wind Force ; and Annual Cycles, .... 

6. Supra-Annual Cycles of Weather and Solar Phenomena, 

7. Temperature, Barometric Range, and Sun-Spots, 

8. Details of Sun-Spot Cycles, ..... 

9. Aurora, Lightning, and Sun-Spots, .... 
10. Of an unfinished Paper on the individual characteristics of every Station employed, 



PAGE 

267 
269 
272 
275 
279 
281 
283 
283 
284 
285 



PART I. 
MEAN SCOTTISH METEOROLOGY. 

Table I.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Barometric Pressure (Reduced to 32° and to the Sea-Level). 



Year. 


January. 


February. 


March. 


April. 


May. ; 


June. 


Ju 


y. 


Obsd. 


Accnmg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accamg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 

Means. 


1856 


29-538 




29-891 




30-195 




29-785 




29-862 




29-900 




29-893 




1857 


29-698 




29-840 




29-804 




29-767 




29-959 




30-020 




29-832 




1858 


30 065 


29-618 


29-998 


29-866 


29-852 


30 OOO 


29-942 


29-776 


29-823 


29-910 


30-032 


29-960 


29-887 


29-862 


1859 


29-864 


29-767 
29791 


29-709 


29-910 
29*860 


29-707 


29-950 
29-890 


29-751 


29-831 
29-811 


30-046 


29-881 
29-922 


29-934 


29-984 
29-972 


30-050 


29-871 
29-916 


1860 


29-529 




29-932 




29-639 




29-978 




29-831 




29-674 




29-988 




1861 


30 038 


29739 


29-681 


29-874 


29-507 


29-839 


30-177 


29 "845 


30-070 


29-904 


29-961 


29-912 


29-619 


29-930 


1862 


29-686 


29789 


30-052 


29-842 


29-698 


29-784 


29-881 


29-900 


29-810 


29-932 


29-733 


29-920 


29-735 


29-878 


1863 


29-492 


29-774 


30-013 


29-872 


29-758 


29 772 


29-819 


29-897 


29-945 


29-914 


29-778 


29-893 


30-076 


29-858 


1864 


30-013 


29739 
29769 


29-886 


29-890 
29-889 


29-634 


29 770 
29755 


30-022 


29-888 
29-902 


29-995 


29-918 
29 -927 


29-802 


29'879 
29-870 


29-934 


29-885 
29-890 


1865 


29-414 




29-801 




29-886 




30-112 




29-836 




30-188 




29-849 




1866 


29-534 


29734 


29-514 


29-880 


29-673 


29-768 


29-935 


29-923 


29-975 


29-918 


29-881 


29-902 


29-911 


29-886 


1867 


29-632 


29716 


29-816 


29-847 


29-875 


29759 


29-591 


29 "924 


29-938 


29-923 


30-050 


29-900 


29-861 


29-888 


1868 


29-740 


29-709 


29-799 


29-844 


29-749 


29-769 


29-852 


29-897 


29-882 


29-924 


30-034 


29-913 


30-058 


29-886 


1869 


29-766 


29 71 1 
29715 


29-677 


29-841 
29-829 


29-890 


29-768 
29776 


29-992 


29-893 
29-900 


29-899 


29-921 
29-919 


30-039 


29-922 
29-930 


29-962 


29-900 
29-904 


1870 


29-842 




29-856 




30-052 




29-993 




29-906 




30-031 




29-945 




1871 


29-706 


29-723 


29-811 


29-831 


29-878 


29795 


29-781 


29-906 


30-063 


29-918 


29-968 


29-937 


29-692 


29-907 


1872 


29-365 


29722 


29-664 


29-830 


29-715 


29 "8oo 


29-874 


29-899 


29-848 


29-928 


29-781 


29'939 


29-927 


29-893 


1873 


29-459 


29701 


30-106 


29-820 


29-818 


29795 


30-046 


29-897 


29-919 


29-923 


29 894 


.29-930 


29-795 


29-895 


1874 


29-748 


29-688 
29-691 


29-867 


29-836 
29-838 


29-988 


29-796 
29-806 


29-741 


29-905 
29-897 


30-001 


29-923 
29-927 


30-075 


29-928 
29-936 


29-890 


29-890 
29-889 


1875 


29-678 




30-090 




30-151 




30-026 




29-884 




29-807 




29-985 




1876 


30-115 


29 '690 


29-663 


29-850 


29-394 


29-823 


29-816 


29-903 


30-158 


29-925 


29-922 


29-929 


29-951 


29-894 


1877 


29-634 


29711 


29-712 


29-841 


29-674 


29-803 


29-819 


29-899 


29-860 


29-936 


29-897 


29-929 


29-762 


29-897 


1878 


29-994 


29-707 


30 099 


29 '835 


29-977 


29797 


29-861 


29-895 


-29712 


29-932 


29-911 


29-927 


30-008 


29-891 


1879 


30-034 


29-720 
29733 


29-512 


29-847 
29'833 


29-899 


29-805 
29-809 


29-748 


29-894 
29-888 


29-983 


29-923 
29-925 


29-709 


29-927 
29-918 


29-698 


29-896 
29-888 


1880 


30-215 




29-553 




30-030 




29-815 




30-084 




29-920 




29-835 




1881 


29-909 


29752 


29-801 


29-822 


29-766 


29-817 


30 010 


29-885 


30-035 


29-932 


29-876 


29-918 


29-834 


29-886 


1882 


30-105 


29758 


29-998 


29*821 


29-767 


29-816 


29-777 


29-890 


30-011 


29-936 


29-818 


29-916 


29-701 


29-884 


1883 


29-728 


29771 


29-834 


29-827 


29-959 


26-814 


29-992 


29-886 


29-909 


29-938 


29-949 


29-912 


29-773 


29-877 


1884 


29-772 


29-769 
29.769 


29-750 


29-828 
29-825 


29-798 


29-819 
29-818 


29-872 


29-889 
29-889 


29-867 


29-937 
29-935 


30-013 


29-914 
29-917 


29-869 


29-873 
29-873 


1885 


29-793 




29-462 




29-997 




29-778 




29719 




29-992 




30-099 




1 886 


29-542 


29770 


30-075 


29-813 


29-890 


29 -824 


29-870 


29-885 


29-888 


29-928 


29-929 


29-920 


29-804 


29-881 


1887 


29-791 


29763 
29764 


30-143 


29821 
29-831 


30-021 


29-826 
29'833 


29-982 


29-885 
29-888 


30 036 


29-926 
29-930 


30-174 


29-920 
29-928 


29-911 


29-878 
29-879 



MEAN SCOTTISH METEOROLOGY. 



189 



Table I. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Barometric Pressure (Reduced to 32° and to the Sea-Level). 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 






















of Observed 
Quantities in 
each Tear. 


Means of the 

Accumulating 

Tears. 


Tear 

repeated. 


Obsd. 


Aeeumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


29-888 




29-766 




30-084 




30-002 




29-628 




29-869 




1856 


30-014 




29-882 




29-803 




30-115 




29-989 




29-894 




1857 


29-943 


29'9Si 


29-898 


29-824 


29-892 


29-944 


29-956 


30-058 


29-703 


29-808 


29-916 


29-882 


1858 


29-850 


29 -948 
29-924 


29-722 


29-849 
29-817 


29-667 


29-926 
29-862 


29-855 


30-024 
29-982 


29-651 


29773 
29743 


29-817 


29-893 
29-874 


1859 


29-575 




29-868 




29784 




29-919 




29-709 




29-786 




1860 


29-774 


29 '854 


29-723 


29-827 


29-936 


29-846 


29-544 


29-969 


30-020 


29736 


29-838 


29-856 


1861 


29-885 


29-841 


29-979 


29-810 


29-620 


29-861 


29-897 


29-898 


29767 


29783 


29-812 


29 '853 


1862 


29-779 


29-847 


29-613 


29-834 


29-657 


29-827 


29-825 


29-898 


29-840 


29781 


^9-800 


29-847 


1863 


30-018 


29-838 
29-858 


29-731 


29-806 
29798 


29-914 


29-805 
29-817 


29-681 


29-889 
29-866 


29-921 


29788 
29-803 


29-879 


29-842 
29-846 


1864 


29-796 




30 131 




29-641 




29-787 




30 015 




29-371 




1865 


29-687 


29-852 


29-555 


29-830 


30-047 


29-800 


29-753 


29-858 


29-672 


29-824 


29-761 


29-848 


1866 


29-856 


29-837 


29-931 


29-806 


29-765 


29-822 


30-230 


29-848 


29-919 


29-810 


29-872 


29-840 


1867 


29-808 


29-839 


29-903 


29-817 


29-772 


29-818 


29-955 


29-880 


29-312 


29-820 


29-822 


29 '843 


1868 


30 015 


29-836 
29-849 


29-590 


29-823 
29-807 


29-969 


29-814 
29-825 


29-730 


29-886 
29 "875 


29-693 


29-780 
29774 


29-852 


29-841 
29-842 


1869 


30-014 




29-937 




29-614 




29-725 




23-937 




29-904 




1870 


29-908 


29-860 


29-930 


29-815 


29-822 


29-811 


29-991 


29-865 


29-906 


29785 


29-871 


29-846 


1871 


29-944 


29-863 


29-682 


29-822 


29-587 


29-812 


29-530 


29-873 


29-464 


29793 


29-698 


29-848 


1872 


29-779 


29-868 


29-839 


29-814 


29-682 


29798 


29-829 


29 - 853 


29-984 


29773 


29-846 


29-839 


1873 


29-782 


29-863 
29 '859 


29-717 


29-816 
29-810 


29 670 


29-792 
29-786 


29-850 


29-851 
29-851 


29-781 


29-831 
29789 


29-842 


29-839 
29-840 


1874 


29-968 




29-981 




29-752 




29-826 




29-958 




29-926 




1875 


29-868 


29-864 


29-753 


29-819 


29-856 


29784 


29-858 


29-850 


29-409 


29793 


29-814 


29-844 


1876 


29-807 


29-864 


30-030 


29-816 


29-802 


29787 


29-386 


29-850 


29-823 


2977S 


29-767 


29-842 


1877 


29-758 


29-862 


29-818 


29-826 


29-615 


29-788 


29-812 


29-829 


29-674 


29777 


29-853 


29-839 


1878 


29-703 


29 '857 
29-851 


29-802 


29-825 
29-824 


30-050 


29-780 
29-792 


30-219 


29-828 
29-845 


30-116 


29773 
29787 


29-873 


29-840 
29-841 


1879 


30-037 




29-896 




29-968 




29-772 




29-740 




29-905 




1880 


29-733 


29-858 


29-986 


29-827 


30-023 


29-799 


29-623 


29-842 


29-765 


29785 


29-863 


29-844 


1881 


29-805 


29 "853 


29-818 


29 '833 


29-820 


29-807 


29-541 


29"833 


29-618 


29784 


29-815 


29-844 


1882 


29-859 


29-852 


29-783 


29 '833 


29-821 


29-808 


29-593 


29-823 


29-997 


29778 


29-850 


29-843 


1883 


29-931 


29-852 
29 '855 


29-905 


29-831 
29'833 


29-929 


29-808 
29-812 


30-062 


29-814 
29-823 


29-661 


29786 
29-782 


29-869 


29-843 
29-844 


1884 


29-977 




29-706 




29-683 




29-829 




30-010 




29-837 




1885 


29-874 


29-859 


29-932 


29-829 


29-793 


29-808 


29-777 


29-823 


29-545 


29789 


29-827 


29-844 


1886 


29-918 


29-859 
29-861 


29-864 


29-832 
29833 


30-025 


29-808 
29-814 


29-660 


29-822 
29-817 


29-688 


29-782 
29779 


29-934 


29-844 
29 "846 


1887 



VOL. XXXV. PART 3. 



2 C 



190 



PROFESSOR C. PIAZZI SMYTH ON 



Table II.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Barometric Range. 



fear. 


Januan . 


Febi 


uary. 


Mai 


ch. 


April. 


May. 


June. 


July. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


1856 


1-897 




1-512 




0-803 




1-185 




1-061 




0737 




0-878 




1857 


1-534 




1-289 




2-021 




1-142 




0-890 




1-039 




0-850 




1858 


1-241 


1 716 


1-427 


1-400 


1-587 


1-412 


1-434 


1-164 


1-339 


C976 


0-702 


0-888 


0-945 


0-864 


1859 


1-855 


1 "557 
I-632 


1-375 


1-409 
1-401 


1-270 


1-470 
1-420 


1-289 


1-254 
1-262 


0-498 


1-097 
0-947 


0-653 


0-826 
0783 


1-083 


0-891 
0-939 


1860 


1-810 




2-079 




1-931 




1-860 




1-228 




1-102 




0-745 




1861 


1-026 


1-667 


1-670 


1 '53 6 


1-430 


1-522 


0-734 


1-382 


0-937 


1-003 


0-694 


0-847 


0-777 


0-900 


1862 


1-451 


1-560 


1-402 


1 '559 


1-322 


1-507 


1-204 


1-274 


0-845 


0-992 


1-074 


0-821 


0-790 


0'88o 


1863 


1-882 


1 '545 


1-385 


I-536 


1-227 


1-481 


1-090 


1-264 


1-108 


0-971 


0-809 


0-856 


0-865 


0-867 


1864 


1-298 


1-587 
1 '555 


1-479 


i-Si7 
1-513 


1-123 


1 '449 
1 '413 


1-032 


1-242 
1-219 


0-669 


0-988 
o-953 


0-731 


0-851 
0-838 


0-924 


0-867 
0-873 


1865 


1-710 




1-715 




1-175 




0-679 




0-884 




0-850 




0-873 




1866 


1-771 


1 '57° 


1-343 


1-533 


1-601 


i'389 


1-218 


1-165 


1-131 


0-946 


0-883 


0-839 


1-139 


0-873 


1867 


1-521 


I-S89 


1-972 


1-516 


1-957 


1-408 


1-326 


1-170 


0-810 


0-963 


1-203 


0-843 


1-055 


0-897 


1868 


1-885 


1-583 
1 '606 


1-889 


1-554 
1-580 


1-824 


1*454 

1-482 


1-541 


1-183 
I-2IO 


1-105 


0-950 
0-962 


0-833 


0-873 

0-870 


1-003 


0-910 
0-918 


1869 


1-723 


1-615 


1-452 


1 '57i 


1-420 


1-478 


1-503 


1-231 


1-121 


o-973 


0-919 


0-874 


0-793 


0-909 


1870 


2-024 




1-540 




1-420^ 




1-197 




1-404 




1-088 




0-805 




1871 


1-940 


1-642 


1-098 


1-569 


1-421 


1 '474 


1-065 


I'229 


0-931 


I - 002 


0-893 


o-888 


0-846 


0-902 


1872 


1-709 


i p 66o 


1-004 


i'539 


1-084 


1-471 


1-016 


I'2I9 


1-335 


0-998 


950 


o-888 


0-517 


0-898 


1873 


2-033 


1-663 


1-737 


1-508 


1-234 


1-448 


0-881 


I "207 


1-042 


I-OI7 


0-934 


0-892 


0-624 


0-876 


1874 


1-466 


1-684 
1-672 


1-663 


1-520 

1-528 


1-525 


1-436 
1-441 


1-754 


1-189 

1-218 


0-866 


I "019 
I "Oil 


1-027 


0-894 
0-901 


0-722 


0-862 
0-854 


1875 


1778 




0-869 




1-264 




1-548 




1-033 




1-256 




1-000 




1876 


1-184 


1-678 


1-260 


1 '495 


1-917 


1 "43 2 


1-397 


1-235 


0-969 


I '012 


0-848 


0-919 


1-050 


0-862 


1877 


1-663 


i'6S4 


1-191 


1-484 


0-996 


1-455 


1-388 


1-243 


1-652 


I - OIO 


1-046 


0-915 


0-936 


0-871 


1878 


1-446 


1-655 


1-007 


1-470 


1-569 


1-434 


1-427 


1-249 


0-943 


1-039 


0-865 


0-921 


0-711 


0-874 


1879 


1-074 


1-646 
1-622 


1-381 


i'45o 
1-447 


1-160 


1-440 

1-428 


1-249 


1-257 
1-257 


0-968 


I-035 
I-032 


0-751 


0-919 
0-912 


1-052 


0-867 
0-874 


1880 


1-262 




1-603 




1-772 




1-451 




1-000 




0-981 




0-875 




1881 


1-855 


1-607 


1-757 


i'454 


1-416 


1-442 


0-786 


1-264 


1-542 


1-031 


1-008 


0-915 


0-721 


0-874 


1882 


1-993 


1-617 


1-758 


i'465 


1-526 


1-441 


1-447 


1-246 


1-317 


I-050 


1-088 


0-918 


1-226 


0-868 


1883 


1-716 


1-631 


1-635 


1-476 


1-734 


i-444 


1-337 


1-253 


0-997 


i'o6o 


0-848 


0-925 


1-054 


0-882 


1884 


2-952 


1-634 
1-679 


1-497 


1-482 
1-482 


1-265 


i - 455 
i'44 8 


1-053 


1-256 
1-249 


1-474 


1-058 
1-072 


0-807 


0-922 
0-918 


0-836 


0-888 
o-886 


1885 


1-929 




1-387 




1-382 




1-177 




0-969 




1-130 




0-807 




1886 


1-254 


1-688 


1-508 


i"479 


1-460 


1-446 


1-573 


1-247 


1-157 


1-069 


0-842 


0-925 


1-088 


0-883 


1887 


1-575 


1-674 


1-463 


1-480 


1-432 


1-446 


1-467 


1-258 


1-223 


1-072 


0-833 


0-922 


1-101 


0-890 






1-671 




1-480 




I-446 




1-264 




1-076 




0-919 




0-897 



MEAN SCOTTISH METEOROLOGY. 



191 



Table II. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Barometric Eange. 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 
Quantities in 
each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


0-812 




1-204 




1-070 




1-033 




1-636 




1-152 




1856 


0-661 




1-101 




1-246 




1-719 




1-338 




1-236 




1857 


1-003 


1736 


0-997 


1152 


1-687 


1-158 


1-872 


1-376 


1-297 


1-487 


1-294 


1-194 


1858 


1-167 


0-825 
0-911 


1-063 


I'lOI 

1-091 


1-236 


1 '334 
1-310 


2-129 


1 -541 
1-688 


1-853 


1-424 
I-S3I 


1-289 


1-227 
1 '243 


1859 


1-080 




1-165 




1-261 




1-641 




1-426 




1-444 




1860 


0-797 


°'94S 


1-172 


1/106 


1-201 


1-300 


1-295 


1-679 


1-459 


1-510 


1-099 


1-283 


1861 


0-944 


0-920 


0-993 


1-117 


1-872 


1-284 


1-513 


1-615 


1-204 


1-502 


1-218 


1*252 


1862 


0-816 


0-923 


1-442 


1-099 


1-660 


1-368 


1-347 


i'6oo 


1-421 


1*459 


1-254 


1-247 


1863 


1-037 


0-910 
0-924 


1-094 


1-142 
i'i37 


1-776 


1-404 
1 "445 


2-056 


1-569 
1-623 


1-264 


i'4S4 
1 '433 


1-207 


1-248 
1*244 


1864 


0-811 




0-887 




1-571 




1-789 




2-013 




1-246 




1865 


1-057 


0-913 


1-165 


1T12 


1-042 


1-458 


0-941 


1-639 


1-511 


1-491 


1-234 


1-244 


1866 


0-650 


0-926 


1-059 


1117 


1-286 


1 '420 


1-381 


1-576 


1-371 


1 '493 


1-299 


1-243 


1867 


0-989 


0-903 


1-411 


I '112 


1-002 


1-409 


1-793 


1-560 


1-704 


1-483 


1-415 


1-248 


1868 


0-923 


0-910 
0-910 


1-563 


I '135 
I-I65 


1-181 


I-378 
i'364 


1-150 


I-578 
1 "547 


2-212 


1-500 
i-55i 


1-330 


1-260 
1-266 


1869 


0854 




1-598 




2-114 




1-631 




1-818 




1-458 




1870 


1-263 


0-907 


1-090 


I -194 


1-295 


1-414 


0-972 


1-553 


1-287 


1-568 


1-175 


1-278 


1871 


0-826 


0-929 


1-101 


i'i88 


1-258 


1-406 


1-810 


1-516 


1-262 


1 '55i 


1-156 


1-272 


1872 


0-702 


0-923 


1-172 


1-183 


1-622 


I-398 


1-949 


1 '534 


1-450 


I- 534 


1-282 


1-265 


1873 


1-254 


0-911 
0-929 


1-049 


1-182 
i'*75 


1-711 


1-410 
1-426 


1-545 


1-649 

I-556 


1-621 


1*529 
1 '534 


1-350 


1-266 
1-270 


1874 


0-714 




1-295 




1-071 




1-383 




1-444 




1-221 




1875 


1-199 


0-918 


1-148 


1-181 


1-612 


1-408 


1-055 


1 '547 


1-596 


i^o 


1-270 


1-268 


1876 


0-890 


0-931 


1105 


1 -179 


1-616 


1-418 


1-908 


1-524 


1-525 


1 '533 


1-326 


1-268 


1877 


1-088 


0-930 


1-232 


1-176 


1-438 


1-427 


1-284 


1 '542 


1-456 


1 '532 


1-206 


1-271 


1878 


1-223 


0-936 
0-948 


1-215 


1 -179 
1-180 


1-501 


1-427 
1 '43° 


1-072 


1 '53° 
1 "512 


1-512 


1 '529 

1-528 


1-180 


1-268 
1-264 


1879 


0-947 




1-013 




1-143 




1-612 




1-574 




1-269 




1880 


1-343 


0-948 


0-944 


1 '173 


1-903 


1-419 


2-008 


i\5i5 


1-782 


i*530 


1-422 


1-264 


1881 


1-124 


0-963 


1-341 


1-165 


1-567 


1-438 


1-473 


1 '534 


1-154 


1 '54° 


1-418 


1-270 


1882 


1-187 


0-969 


1-365 


1-171 


1-548 


1-442 


1-679 


i*532 


1-711 


1-526 


1-401 


1-276 


1883 


0-747 


0-977 
0-969 


1-231 


1-178 
i'i8o 


1-721 


1-446 
1*456 


1-412 


1 '537 
1 '533 


1-450 


1 '532 
1-529 


1-370 


1-280 
1-283 


1884 


1-151 




1-124 




1-618 




1-524 




1-613 




1-318 




1885 


0-791 


°*975 


1-217 


1 '178 


1-654 


1-461 


1-523 


1 '533 


2-636 


i*532 


1-392 


1*285 


1886 


1-106 


0-969 


1-472 


1-179 


1-441 


1-467 


1-760 


i*532 


1-416 


1-568 


1-357 


1-288 


1887 




0-974 




i-i88 




1-466 




1 '539 




1*563 




1 -290 





192 



PROFESSOR C. PIAZZI SMYTH ON 



Table III. —SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Temperature. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


July. 


Obsd. 


\ccumg. 
Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 




°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


1856 


34-3 




39-6 




39-4 




44-3 




467 




53-3 




56-4 




1857 


35-7 




39 3 




39-2 




427 




49-8 




57'4 




58-0 




1858 


39-3 


35'° 


35-8 


39 "4 


39-5 


39'3 


43-8 


43 '5 


49-5 


48-2 


58-9 


55'4 


. 56-0 


57'2 


1859 


39-6 


3 6 '4 
37 '2 


40-5 


38-2 
38-8 


43-0 


39 "4 
4°'3 


41-9 


43 '6 
43 - 2 


51-9 


487 
49 '5 


56-6 


56-S 
S6-S 


59-0 


S 6-8 
57 '4 


1860 


35-5 




34-0 




38-4 




41-5 




50-2 




53-0 




573 




1861 


36-3 


3 6- 9 


39-5 


37-8 


41-1 


39 '9 


45-4 


42-8 


49-1 


49-6 


57-2 


SS'8 


56-8 


57 '3 


1862 


38-4 


3 6-8 


40-1 


38-1 


37-8 


40T. 


44-6 


43 '3 


511 


49'5 


52-4 


S6-i 


53-8 


57 '2 


1863 


38-5 


37 "o 


41-2 


38-4 


42-9 


39 - 8 


44-4 


43*5 


48-6 


49 '8 


54-0 


55'5 


56-1 


56-8 


1864 


36-2 


37 - 2 
37'i 


33-5 


38-8 
38-2 


37-5 


40 '2 

39'9 


46-1 


43 ' 6 
43 "9 


50-0 


49 -6 
497 


53-4 


55 '4 
SS"i 


567 


567 

S67 


1865 


34-6 




33-9 




37-3 




46-5 




50-9 




57 1 




58-4 




1866 


39-4 


36 -8 


36-7 


377 


38-0 


39 '6 


44-0 


44-1 


47 '9 


49-8 


561 


55 '3 


56-9 


56-8 


1867 


31-8 


37 - i 


41-4 


37 '6 


36-2 


39'5 


45-3 


44'i 


47-5 


49-6 


54-3 


55'4 


54-8 


56 '9 


1868 


37-5 


36-6 


41-6 


38-0 


42-8 


39'2 


46-0 


44'2 


51-4 


49 '4 


55-6 


55 '3 


60-4 


567 


1869 


40-4 


367 
37'° 


41-9 


38-2 
38-5 


37-8 


39'5 
39 '4 


46-9 


44 '4 
44'5 


45-1 


49-6 
49 '3 


53 1 


55'3 
55'2 


59-3 


57'° 
57'i 


1870 


35-9 




35-2 




39-5 




46-9 




50-5 




55-6 




59 -6 




1871 


33 8 


36 - 9 


41 '0 


38-3 


42-6 


39"4 


42-5 


447 


50-3 


49 '4 


53-4 


S5 - 2 


577 


S7'3 


1872 


39-0 


367 


41-2 


38-4 


41-8 


39"° 


45-2 


44-6 


47-4 


49 '4 


55-1 


55-i 


59-3 


57 '3 


1873 


39-2 


3 6-8 


35-4 


38-6 


39-7 


397 


44-8 


44-6 


46-9 


49 '3 


55-9 


55'* 


58-5 


57-4 


1874 


40-5 


37 '0 
37'2 


38-8 


38H 
38-5 


43-3 


397 
39 "9 


46-7 


44-6 
447 


471 


49'2 
49'° 


54-8 


5S'i 
55"i 


59-4 


57 '5 
57 -6 


1875 


39-7 




36-3 




40-0 




46-5 




517 




54-0 




57-1 




1876 


39-2 


37 "3 


36 9 


38-3 


37-6 


39 '9 


437 


44-8 


48-9 


49 '2 


55-0 


55'i 


58-4 


57 "6 


1877 


37-6 


37 '4 


39-5 


38-3 


38-4 


39-8 


41-4 


447 


45-9 


49 '2 


55-1 


5S'i 


56-3 


57'6 


1878 


38-0 


37 "4 


41 '5 


38-3 


40-3 


397 


45-5 


44-6 


50-3 


49'° 


55-5 


55-i 


59-5 


57 "6 


1879 


31-0 


37 "4 
37'i 


34-0 


38-S 
38-3 


37-5 


397 
39 '6 


41 


44-6 

44 '5 


46-2 


49'° 
49 '° 


53-2 


55 - i 
55 ° 


54-8 


57 "6 

57 '5 


1880 


36-8 




417 




41-2 




447 




49-0 




54-9 




56 7 




1881 


28-2 


37'i 


34-4 


38-4 


37-1 


397 


42-2 


44 '5 


50-4 


48-9 


52-9 


55"° 


567 


57 "5 


1882 


41-3 


36-8 


42-3 


38-3 


43-0 


39'6 


43-1 


44*4 


497 


49 "o 


53-5 


54'9 


57'3 


57 "5 


1883 


38-3 


37'o 


40-3 


38-4 


36-0 


397 


44-6 


44 '4 


47-8 


49 "o 


53-5 


54 - 9 


55-9 


57 '4 


1884 


403 


37 - ° 
37'i 


39-2 


38-S 
38-S 


41-0 


39 "6 
39 '6 


43 3 


44'4 
44'3 


48-6 


49 "o 
49'° 


54-2 


S4'8 
54-8 


57 3 


57 '4 
57 '4 


1885 


35-9 




38-5 




387 




43-9 




45-2 




53-6 




57-5 




1886 


34-1 


37"i 


34-5 


38-5 


37-3 


39 '6 


431 


44'3 


47-0 


48-9 


52-9 


54-8 


56-4 


57 - 4 


1887 


37-5 


37 - o 
37 ° 


39-7 


38-4 
38-4 


38-6 


39 "5 
39 '5 


42-3 


44 '3 
44-2 


48-9 


48-8 
4 8-8 


57-6 


547 
54-8 


59-3 


57 - 4 

57 '4 



MEAN SCOTTISH METEOROLOGY. 



193 



Table III. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OE. 

Mean Temperature. 



August. 


September. 


October. j 


November. 


December. 


Mean Month 


Successive 
























of Observed 
Quantities in 
each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 




57-1 




50-9 




48-8 




397 




37-9 




457 




1856 


60-0 




56-1 




49-6 




437 




44-9 




48-0 




1857 


57-9 


58-6 


54-5 


53'5 


44-9 


49 "2 


39-4 


417 


39-9 


41-4 


46-6 


46-8 


1858 


57-8 


58-3 
58-2 


52-3 


53-8 
53 '4 


45-8 


47-8 
47 '3 


39-4 


40-9 
4<r6 


34-0 


4° - 9 
39 "2 


46-8 


46-8 

46-8 


1859 


54-4 




50-2 




46-0 




39-1 




34-1 




44-5 




1860 


57 '4 


57 '4 


537 


52-8 


49-5 


47 "o 


38-5 


4° '3 


38-0 


38 - 2 


46-9 


4 6 '3 ! 


1861 


56-0 


57 - 4 


53-4 


53'° 


47-1 


47 '4 


37-1 


40 '0 


41-8 


38T 


46-1 


46-4 


1862 


55-7 


57 '2 


50-1 


53 '0 


46-8 


47 '4 


43-1 


39 '6 


40-8 


387 


46-8 


46-4 


1863 


54-4 


57 'o 
5^7 


52-4 


52-6 
52 '6 


45-8 


47 '3 
47 'i 


40-9 


40 '0 
40T. 


39 4 


38-9 
39 '0 


45-5 


46-4 
46-3 


1864 


56-1 




58-0 




46-0 




41-4 




42-9 




46-9 




1865 


55-0 


567 


51-4 


53*2 


48-6 


47-0 


41-2 


40 '2 


40-6 


39 "4 


46-3 


46-4 


1866 


57-4 


56'5 


53-4 


53'° 


46-4 


47 "2 


41-6 


40'3 


38-8 


39 '5 


457 


46-4 ; 


1867 


58-5 


56-6 


53-2 


53 'o 


44-8 


47'i 


39-2 


40-4 


40-6 


39 '4 


47-6 


46-3 


1868 


56-1 


56-8 
567 


537 


53'° 
53 - i 


47-3 


46-9 
47-0 


40-4 


40 - 3 

4° "3 


34-9 


39 '5 
39 '2 


46-4 


46-4 
46-4 


1869 


58-0 




53-6 




46-3 




39-1 




33-5 




46-1 




1870 


58-9 


56-8 


52-2 


53'i 


47-2 


46-9 


38-6 


4C2 


38-0 


38-8 


46-4 


46-4 


1871 


56-5 


56-9 


51-5 


53 - i 


45-8 


46-9 


41-3 


40 - 2 


38-3 


38-8 


46-9 


46-4 


1872 


56-4 


56-9 


51-4 


53"° 


44-3 


46-9 


41 '2 


40 - 2 


42-5 


387 


46-4 


46-4 


1873 


55-9 


56 '9 
56-8 


52-8 


52'9 
52-9 


46-5 


467 

467 


41-1 


4°'3 
40 "3 


30-9 


38-9 
38-5 


46-5 


46-4 

46 '4 


1874 


58-1 




54-4 




47-0 




39-2 




38'9 




46-9 




1875 


57-8 


S6-9 


51-8 


53'° 


49-8 


467 


407 


4°'3 


40-0 


38-5 


46-6 


46-4 


1876 


55-1 


5 6 '9 


50-5 


52'9 


467 


46-9 


42-5^ 


40-3 


39-3 


38-6 


457 


46-5 


1877 


58-6 


56-8 


54-3 


52-8 


48-9 


46-9 


38-0 


4° '4 


307 


38-6 


46-8 


46 ' 4 


1878 


56-0 


S6-9 
56-9 


51-5 


52-9 
52-8 


46-0 


46-9 
46-9 


40-5 


40-3 
4°"3 


347 


38-3 
38-1 


43-9 


46-4 
46-3 


1879 


59-4 




55-2 




42-4 




38-5 




36-6 




46-4 




1880 


53-5 


57 '0 


52-4 


52-9 


44-8 


467 


45 -a 


40 '2 


38-3 


38-1 


447 


46-3 


1881 


57-3 


56-8 


51-8 


52'9 


48-0 


467 


39-1 


40-4 


33-6 


38-1 


467 


46-3 : 


1882 


56-2 


56-9 


52-8 


52-8 


46-4 


467 


40-4 


40-4 


39-4 


37 '9 


46-0 


46 '3 


1883 


58-4 


56-8 
56-9 


54-2 


52-8 
52-9 


46-9 


467 
467 


40-2 


40 -4 
4°'3 


367 


38-0 
37 '9 


467 


46'3 
46 '3 


1884 


53-6 




50-8 




42-4 




40-3 




38-2 




44-9 




1885 


56-2 


56-8 


52-2 


52-8 


49-5 


46-6 


42-8 


4° '3 


33-0 


37 '9 


44-9 


46 '2 


1886 


56-4 


56-8 
5 6-8 


515 


52-8 
52-8 


44-1 


467 
46-6 


39-6 


40-4 
4°'4 


36-1 


37-8 
377 


46-0 


1 46 - 2 
46 - 2 


1887 



VOL. XXXV. PART 3. 



2 D 



194 



PROFESSOR C. PIAZZI SMYTH ON 



Table IV.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Mean Daily Range of Temperature. 



Tear. 


January. 


February. 


Mai 


eh. 


April. 


May. 


June. 


July. 


Obsd. 


Vccumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accnmg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accnmg. 
Means. 




°F. 


•F. 


° F. 


°F. 


° F. 


*F. 


°F. 


°F. 


F. 


°F. 


°F. 


°F. 


F. 


°F. 


1856 


7-3 




8-8 




13-2 




) 13-3 




14-2 




14'4 




167 




1857 


8-2 




10 




9-5 




12-0 




14-4 




17-2 




14-1 




1858 


9-4 


7 -8 


107 


9'4 


11-9 


"'4 


15-3 


I2'6 


14-8 


*4'3 


16-4 


15-8 


147 


IS '4 


1859 


9-6 


8-3 
8-6 


9-8 


9-8 
9-8 


10-9 


"'5 
. "'4 


135 


i3 - 5 
i3'5 


19-7 


H'S 

i5'8 


161 


i6 - o 
16 - o 


14-3 


IS'2 

iS'o 


1860 


8-1 




10-7 




11-5 




14-9 




15-0 




13-3 




14-5 




1861 


8-2 


8-5 


9-3 


IO'O 


11-4 


ii -4 


14-1 


i 3 -8 


15-6 


15-6 


13-6 


iS'S 


13-6 


14-9 


1862 


7 1 


8-5 


8-6 


9'9 


9 3 


n-4 


137 


13-8 


14'1 


iS-6 


12'6 


15-2 


13-1 


I4'6 


1863 


8-7 


8 '3 


10-9 


97 


11-2 


Il'i 


13-4 


i 3 -8 


14-1 


15-4 


13-2 


14-8 


16-8 


14 4 


1864 


9-1 


8-3 
8 - 4 


HI 


9-8 

IO'O 


11-0 


n't 

n"i 


14-5 


I3'8 

13 "9 


161 


15-2 
*5'3 


13-7 


14 - 6 
I4'5 


147 


147 
147 


1865 


9-2 




9-3 




10-8 




16 1 




14-0 




17-3 




157 




1866 


8-9 


8-5 


7-8 


9"9 


11-4 


n't 


13-1 


14-1 


17-9 


15-2 


15'8 


14-8 


14-0 


14*8 


1867 


9-7 


8-5 


9-5 


97 


11-4 


n't 


11-5 


14 'O 


12-2 


15*4 


13-9 


14 '9 


12-9 


147 


1868 


90 


8-6 


9-9 


97 


12-0 


ii*i 


12-9 


13-8 


14-9 


15-2 


16-3 


14-8 


18-2 


147 


1869 


8-1 


8-6 
8-6 


9-8 


97 
97 


12-0 


II "2 

it's 


15-8 


137 
13 "9 


14-7 


15-2 


15-8 


14-9 
150 


15-8 


14 '9 
14-9 


1870 


8-2 




9-3 




12-3 




15-6 




14'2 




14-9 




15-5 




1871 


8-9 


8-6 


8-2 


97 


12-9 


""3 


13-1 


i4'o 


17-5 


i5'i 


15-3 


15 'o 


13-9 


150 


1872 


8-5 


8-6 


8-9 


9 -6 


10-9 


n*4 


12-6 


13 "9 


13-5 


I5'2 


13-8 


iS'o 


14-8 


14-9 


1873 


9 


8-6 


11*1 


9-6 


11-2 


n- 4 


14-7 


13-8 


14-6 


iS'i 


15-6 


14-9 


15-1 


14 '9 


1874 


9-9 


8-6 
87 


11-3 


9-6 
97 


12-0 


ii - 4 
tt'4 


15-4 


i3"9 
13 '9 


14-2 


i5 - o 


18-8 


iS'o 

IS '2 


157 


14 '9 
iS'o 


1875 


9-7 




9-5 




11-5 




17-3 




15-3 




15-9 




16 9 




1876 


97 


87 


9-8 


97 


10-6 


ii- 4 


13-1 


14-1 


16-6 


iS'o 


177 


I5'2 


16-0 


iS'o 


1877 


9-6 


8 8 


10-6 


97 


12-5 


ii - 4 


11-9 


14-1 


14-1 


iS'i 


14-9 


iS'3 


12-4 


iS'i 


1878 


9-7 


8-8 


9-6 


9-8 


12-4 


ii'4 


13-9 


14*0 


14-5 


i5"i 


16-5 


15 '3 


16-0 


iS'o 


1879 


10-5 


8- 9 
8-9 


9-6 


9-8 

9-8 


11-0 


""5 
n'4 


12-4 


14 - o 

13 '9 


16-2 


iS'o 
i5'i 


13-6 


iS'3 
iS'3 


11-9 


iS'o 
14-9 


1880 


9-5 




10-0 




14-6 




14-1 




16-5- 




17-2 




14-4 




1881 


12-6 


9 -o 


9-2 


9-8 


12-7 


n-6 


15-8 


I3'9 


18-0 


15 - 2 


16-3 


iS'4 


14-0 


14-9 


1882 


9 2 


9' 1 


10-5 


97 


12-3 


n-6 


13-6 


14*0 


18-3 


iS'3 


15-8 


IS '4 


14 6 


14-8 


1883 


9 


9't 


9-9 


9-8 


12-5 


n-6 


14-7 


14 'O 


157 


i5'4 


16-2 


15 '4 


14-5 


14 '8 


1884 


9-0 


9'i 
9'i 


9-8 


9-8 
9-8 


11-5 


117 
117 


14-6 


14 "o 
14*0 


16-1 


IS "4 

IS '4 


16-0 


IS '4 

iS'S 


14-4 


14-8 
14-8 


1885 


8-6 




11*1 




13-2 




14-6 




14-2 




16'6 




17-5 




1886 


9-9 


9'i 


9-5 


9-8 


11-2 


n 7 


14-8 


i4'o 


14-5 


IS '4 


16-4 


iS'S 


15-6 


14 '9 


1837 


9-0 


9'* 


11-3 


9-8 


13-5 


117 


15-9 


14-1 


16-4 


i5'3 


19-0 


iS'S 


16-4 


i4'9 






9'i 




9'9 




n-8 




14-1 




IS '4 




i5'6 




iS'o 



MEAN SCOTTISH METEOROLOGY. 



195 



Table IV. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Daily Range op Temperature. 



August. 


September. 


October. 


November. 


December. 


Mean Month 
of Observed 

Quantities in 
each Year. 


Successive 

Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


°F. 
14-6 


°F. 


°F. 
13-2 


°F. 


°F. 

10-9 


°F. 


°F. 
10-0 


°F. 


°F. 
9'3 


°F. 


° E. ; 

12-2 


°F. 


1856 


14-1 




12-8 




11-4 




9 1 




8'5 




11-8 




1857 


16-0 


14-4 


14-6 


13 -o 


12-4 


II - 2 


97 


9-6 


8'3 


8-9 \ 


12-8 


I2'0 


1858 


147 


14-9 
14-9 


13-6 


i3'5 
i3'5 


12-0 


n-6 
117 


10-4 


9-6 
9 -8 ' 


87 


87 
87 


12-8 


12-3 
12*4 


1859 


12-8 




13-8 




10-9 




81 




8-1 




11-8 I 




1860 


110 


14 '4 


11-0 


13-6 


11-16 


" - 5 


10-9 


9'5 


9 5 


8-6 


11-6 


12 -3 


1861 


126 


13 '9 


14-1 


13-2 


127 


"•5 


11-0 


97 


87 


87 


11-5 


I2 - 2 


1862 


14-0 


137 


12-2 


i3'3 


10-6 


117 


9-8 


9'9 


9-8 


87 


12-1 


I2 - I 


1863 


16-1 


137 
i4 - o 


13-8 


13-2 
13-2 


11-3 


n-6 
ix'5 


10-6 


9 '9 
10 - o 


77 


8' 9 
87 


12-5 


12 - I 
I2'I 


1864 


133 




15-9 




12-2 




10-9 




8'4 




12-8 




1865 


127 


13 '9 


127 


i3'5 


11-3 


n-6 


10-1 


IO'O 


9-5 


87 


12-1 


I2 - 2 


1866 


137 


13-8 


117 


i3'4 


11-9 


n-6 


10-4 


10 


9-2 


8'8 


11-5 


12 - 2 


1867 


14-0 


13-8 


12-6 


13 '3 


12-8 


11 -6 


9-3 


IO - I 


8-8 


8'8 


12-6 


12*1 


1868 


16-3 


i 3 -8 
i4 - o 


12-0 


13-2 
I3' 1 


111 


117 
116 


10'3 


IO'O 
IO'O 


9-9 


8'8 
8-9 


12-6 


12*2 
12 - 2 


1869 


17-8 




15-5 




12-9 




107 




97 




13-0 




1870 


15-8 


14*2 


13-2 


I3'3 


11-9 


117 


9-8 


IO'I 


10-1 


8-9 


12-6 


12 '2 


1871 


13-9 


14 '3 


11-3 


!3'3 


11-3 


117 


9-6 


IO'I 


8-4 


9-0 


11-5 


12 -3 


1872 


13-3 


14 '3 


14 '3 


13-2 


12-9 


117 


10-2 


IO'O 


9-6 


90 


11-9 


I2"2 


1873 


14-6 


I4'3 
i4'3 


13-2 


13-2 
13 '2 


13-2 


n-8 
11-9 


9-5 


IO'O 
IO'O 


11-4 


9'o 
9'i 


13-3 


I2'2 

12-3 


1874 


137 




14'4 




10-2 




10-2 




9-3 




12-8 




1875 


167 


14*2 


12-4 


13 "3 


9 6 


n-8 


97 


IO'O 


7'4 


9-1 


12-4 


12-3 


1876 


12-2 


14 '4 


14-6 


133 


12-5 


117 


101 


IO'O 


9-4 


9"i 


12-1 


12 -3 


1877 


14-4 


I4"3 


13 3 


13 '3 


10-9 


117 


10-1 


IO'O 


10-9 


9"i 


127 


I2"3 


1878 


13-2 


I4"3 

14 '2 


13-6 


13 '3 
13 '3 


143 


117 
11 -8 


10-3 


IO'O 
IO'O 


117 


9-1 
9"3 


12-4 


12 '3 
12-3 


1879 


16-2 




15-6 




14-2 




127 




10-5 




13 8 




1880 


13-9 


i4'3 


12-8 


13 - 4 


11-8 


11-9 


11-2 


IO'I 


10-1 


9 '3 


13-2 


12 - 4 


1881 


15-2 


14 - 3 


14 6 


i3"4 


117 


11-9 


110 


IO'2 


9-9 


9 '3 


13-1 


12 "4 


1882 


14-5 


i4'3 


13-9 


13 '4 


]3-4 


11-9 


10'8 


I0'2 


10-2 


9 - 4 


12 -9 


12 - 4 


1883 


16-2 


*4'3 
14-4 


15-0 


i3'5 
i3"5 


12-4 


119 
119 


11-2 


102 

10-3 


9'4 


9'4 
9 '4 


13-0 


12-4 
12 5 


1884 


15-3 




14-4 




117 




10-2 




10-3 




13-1 




1885 


14-6 


14-4 


14 6 


13 \5 


10-8 


119 


10-6 


103 


10-6 


9 '4 


12-8 


I2\5 


1886 


16-8 


14 "4 
H'5 


14-1 


13-6 
13-6 


13-1 


n-g 

119 


97 


10-3 
io'3 


10 '1 


9 - S 
9'5 


13-8 


12 'S 

12-5 


1887 



196 



PROFESSOR C. PIAZZI SMYTH ON 



Table V.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Mean of Black Bulb in the Sun, or by Day. 



Year. 


January. 


February. 


March. 


Api 


il. 


May. 


June. 


July. 


Obsd. ' 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 




°F. 


F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


°F. 


1856 






























1857 


56-7 




62-0 




58-5 




70 2 




81-0 




98-0 




92-5 




1858 


52-6 




59-3 




68-6 




77-5 




81-3 




97-4 




89-8 




1859 


54-6 


54 '6 
54'° 


59-3 


60 -6 

6o"2 


65-1 


63-6 
64 "i 


71-0 


73'8 
72 '9 


918 


81-2 
847 


95 3 


977 
96-9 


92-0 


91 "2 
91-4 


1860 


48-4 




57-0 




66-5 




767 




81-5 




80-8 




90-8 




1861 


46-6 


53'i 


55-4 


59 - 4 


62-1 


647 


737 


73'8 


79-9 


83-9 


89-0 


92-9 


86-3 


91 '3 


1862 


47-9 


51*8 


57-5 


58-6 


56 2 


64-2 


707 


73-8 


77-8 


83-1 


78-4 


92 - I 


80-8 


9°'3 


1863 


47-6 


Si'i 


56-3 


58'4 


63-6 


62-8 


67-6 


73'3 


74-8 


82-2 


82-8 


89-8 


89-2 


887 


1864 


48-0 


SO -6 
5° '3 


54-0 


S 8'i 
57 '6 


58-9 


62 "9 

62 - 4 


72-9 


72'5 
72-5 


82-6 


8l "2 

81-3 


827 


88-8 
88 -o 


89-3 


88-8 
88 8 


1865 


46-8 




49-5 




61-3 




75-6 




79-1 




91-6 




90 7 




1866 


50-6 


49 '9 


56-6 


567 


63-4 


62-3 


70-4 


72-9 


81-6 


8n 


89-8 


88-5 


881 


89-0 


1867 


46-5 


50 -o 


58-6 


56'7 


62-6 


62-4 


68-6 


72*6 


74-1 


8ri 


85-8 


88-6 


85-6 


89-0 


1868 


47-8 


497 


56-2 


56 '9 


65-1 


62-4 


72-2 


72-3 


81-5 


80-5 


88-5 


88-3 


97-5 


88 -6 


1869 


48-9 


49 '5 
49 '5 


57-3 


5 6-8 
56-8 


65-0 


627 
62-8 


77-6 


72 '3 

727 


77-3 


80 -6 
80-3 


877 


88-3 
88-3 


92-4 


89H 
89-6 


1870 


47-1 




52-1 




66-2 




771 




81-5 




91-2 




95-6 




1871 


45-2 


49 '3 


55-0 


56-5 


67-8 


63-1 


72-5 


73'° 


89-8 


80-4 


92-8 


88-5 


94-8 


90 'o 


1872 


48-8 


49'° 


567 


56 '4 


65-4 


63 '4 


757 


73 '0 


817 


81 -o 


89-3 


88-8 


97-0 


90-4 


1873 


48-8 


49'° 


56-4 


56-4 


63-2 


63 '5 


76-9 


73'i 


83-2 


8ri 


91-0 


88-8 


92-9 


90-8 


1874 


50-6 


49 '0 
49-1 


56-3 


56-4 
56 '4 


64-5 


63 '5 
63-6 


74-8 


73 '3 
73 "4 


81-0 


8l -2 

81-2 


93-8 


88-9 
89-2 


94-2 


90-9 
gri 


1875 


49-5 




51-2 




62-6 




787 




80-4 




92-2 




92-4 




1876 


50 '4 


49 '1 


55-3 


56-i 


58-1 


63 '5 


72-6 


737 


86-3 


81-2 


92-4 


89-4 


93-8 


91 '2 


1877 


48-4 


49 '2 


56-2 


56-1 


64-9 


63-2 


657 


73 '6 


78-6 


81 *4 


89-3 


89-S 


85-3 


9 I- 3 


1878 


507 


49-1 


57-3 


56-i 


66-2 


°3 '3 


72-2 


73 "3 


82-4 


81-3 


92-0 


89-S 


96-5 


91 - o 


1879 


45-0 


49 '2 
49'° 


49-1 


56 '2 

55'9 


61-0 


63 "4 
63 '3 


71-2 


73 "2 
73' 1 


79-5 


81 -3 

8l -2 


85-3 


89-6 
89-4 


837 


9i '3 
90-9 


1880 


487 




60-5 




707 




76-3 




85-8 




94-6 




95-0 




1881 


47-1 


49'° 


52-4 


56-0 


64-1 


63-6 


76-8 


73 '3 


86-4 


8l-4 


907 


897 


87-8 


91 -I 


1882 


51-4 


48-9 


58-8 


55 '9 


661 


637 


72-2 


73 '4 


87-4 


8r6 


89-6 


897 


92-3 


91 - o 


1883 


48-6 


49'° 


56-0 


56-0 


65-2 


63-8 


72-9 


73 '4 


81-0 


81-9 


89-9 


897 


92-5 


91 - o 


1884 


48-7 


49-0 
49 '0 


55-4 


56-0 
56-0 


61-9 


63-8 
637 


74-5 


73 "3 
73 '4 


81'2 


81 -8 
8r8 


897 


897 
897 


897 


91 -I 

91 'O 


1885 


43-7 




57-1 




66-4 




73-5 




76-5 




90-2 




92-9 




1886 


45-2 


48-8 


54-2 


56-0 


62-9 


63-8 


77-3 


73 '4 


78-2 


81 -6 


93 '2 


897 


91-8 


91 'O 


1887 


476 


487 
487 


60-3 


56-0 

56-i 


69-1 


63-8 
64 "O 


77-8 


73'5 
737 


86-0 


81-5 
817 


97-1 


89-8 
90 "i 


99-6 


91-1 
9i '4 



MEAN SCOTTISH METEOROLOGY. 



197 



Table V. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Mean of Black Bulb in the Sun, or by Day 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 


Means of the 
Accumulating 


Year 
repeated. 






















Quantities in 


Obsd. 


Aecumg. 
Means. 


Obsd. 


Aecumg. 
Means. 


Obsd. 


Aecumg. 
Means. 


Obsd. 


Aecumg. 
Means. 


Obsd. 


Aecumg. 
Means^ 


each Year. 


Years. 




°F. 


° F. 


F. 


F. 


° F. 


°F. 


F. 


F. 


F. 


°F. 


F. 


F. 


1856 


971 




83-6 




73-6 




59-2 




55-3 




74-0 




1857 


937 


95 '4 


88-0 


8 S -8 


67-7 


70 "6 


591 


59'2 


50-6 


53 'o 


73-8 


73 '9 


1858 


91-1 




83-4 




70-1 




56-1 




46 4 




73-0 








94 -o 




85-0 




7°'S 




58-1 




50-8 




73 ' 6 


1859 


84-6 


gi'6 


81-7 


84-2 


68-1 


69-9 


53-2 


56-9 


45-0 


49 '3 


69-5 


72 '6 


1860 


81-3 


89-6 


79-6 


83-3 


70-4 


70 'O 


55-3 


56-6 


51-4 


497 


69-2 


7i '9 


1861 


82 2 


88-3 


82-3 


8 3 -i 


68-4 


697 


53-4 


56-0 


49-4 


497 


67-1 


71-1 


1862 


837 


877 


73-9 


8i-8 


65-0 


69 'o 


55-7 


56-0 


48-8 


49 -6 


67-4 


70 '6 


1863 


877 


877 


80-2 


81 -6 


66-0 


687 


55 3 


55 "9 


46-7 


49'2 


68-8 


7° '4 


1864 


82 6 


87-1 


89-0 


82-4 


66-2 


68-4 


57-5 


5<5'i 


52-6 


49-6 


70-2 


7° '3 


1865 


82-8 


867 


77-4 


81-9 


68-4 


68 -4 


58-2 


56-3 


49-8 


49 ' 6 


69-8 


70-3 


1866 


86-8 


867 


77-8 


SI'S 


671 


68-3 


57-3 


56-4 


49-8 


49 "6 


68-4 


7C1 


1867 


85-1 


86-6 


76-9 


8l -2 


65-3 


68 -o 


51-9 


56-0 


49-4 


49 '6 


69-8 


70 'i 


1868 


90-4 


86-8 


77 - 5 


80'9 


65-7 


6 7 '8 


53-6 


55-8 


45-9 


49 "3 


69-9 


70*1 


1869 


98-8 


877 


86-5 


81 -3 


69-8 


68 -o 


56-2 


55 '9 


43 4 


48-9 


72-1 


70*2 


1870 


95-0 


88-2 


84-9 


81 -5 


69-5 


68-i 


55-2 


55-8 


48-8 


48-9 


72 6 


70 '4 


1871 


91-2 


88-4 


76-1 


81 '2 


68-7 


68-i 


54-9 


55-8 


46-8 


48-8 


71-0 


70-4 


1872 


86-9 


88-3 


83-0 


81 - 3 


66'0 


68 -o 


52 6 


55 " 2 


49-8 


48-3 


70-9 


7° '4 


1873 


87-0 


88-2 


78-9 


8l '2 


65-8 


67 '9 


52-3 


55 '4 


41-4 


48-4 


70-0 


7° '4 


1874 


87-1 


88-2 


80-1 


8ri 


62-9 


67-6 


51-6 


55 ' 2 


47-4 


48-4 


69-7 


70 '4 


1875 


93-0 


88-4 


81-4 


8ri 


67-7 


67-6 


55-2 


55' 2 


46-0 


48-2 


71-0 


7° "4 


1876 


81-4 


88-i 


81-7 


81 -i 


67-8 


67-6 


57-9 


55 '3 


48-1 


48-2 


68-8 


7° '3 


1877 


90-3 


88-2 


84-8 


81-3 


68-2 


677 


54-0 


55 '3 


43-5 


48-0 


71-5 


70-4 


1878 


89 3 


88-2 


83-1 


81-4 


74-6 


68 -o 


58-5 


55 "4 


46-4 


47 '9 


68-9 


7° '3 


1879 


961 


88 -5 


89-9 


817 


70-2 


68 -o 


56-2 


55 '4 


47 3 


47 '9 


74-3 


7° "5 


1880 


86-5 


88 -s 


79-7 


817 


68-2 


68-i 


57-0 


55 '5 


47-6 


47 '9 


70-4 


70-5 


1881 


92-5 


88-6 


80-5 


81 -6 


67-5 


68 -o 


53-6 


55 '4 


41-9 


477 


71-2 


7°' 5 


1882 


88-8 


88-6 


82-2 


81 -6 


72-5 


68-2 


56-4 


55'5 


48-6 


477 


71-2 ! 


7° '5 


1883 


92-9 


88-8 


86-7 


81 -8 


68-3 


68-2 


54-1 


55 "4 


44-8 


47-6 


707 


7° '5 


1884 


85-5 


887 


82-0 


8i-8 


67-4 


68-2 


52-2 


55 '3 


49 3 


477 


697 


7° '5 


1885 


91-6 


88-8 


82-7 


81 -8 


69-1 


68-2 


60-8 


55'5 


46-8 


47 -6 


71-2 


7°'5 


1886 


93-3 




84-7 




73 4 




53-4 




47-2 




74-2 




1887 




88-9 




81-9 




68-4 




55 '4 




47 '6 




707 





VOL. XXXV. PART 3. 



2 E 



IDS 



PROFESSOR C. PIAZZI SMYTH ON 



Table VI.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean of Black Bulb during Night. 



Year. 


January. 


Febr 


nary. 


March. 


April. 


May. 


June. 


July. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 




°F. 


° F. 


°F. 


F. 


F. 


F. 


F. 


F. 


° F. 


F. 


F. 


F. 


°F. 


°F. 


1856 






























1857 


28-8 




31-7 




31-5 




33 3 




387 




45-5 




45-9 




1858 


30-9 




247 




29-2 




31-3 




37-8 




45-4 




43-6 




1859 


30-3 


29-8 
30-0 


30-8 


28-2 

29'I 


32 9 


3° '4 
31-2 


28-8 


32 '3 
3i'i 


34-1 


38-2 
36 - 9 


42-7 


45 "4 
44"5 


45 9 


44-8 
45 "o 


1860 


26-7 




24 1 




27-4 




297 




37-8 




42-2 




45-5 




1861 


28-7 


29 - 2 


31-0 


27-8 


31-6 


3° "2 


33-5 


30-8 


36-0 


37'i 


46 


44-0 


44-9 


45 "2 


1862 


31-6 


29'I 


32-0 


28-5 


29-4 


3°'5 


33-4 


3i'3 


38-9 


36-9 


41-3 


44 - 4 


42-3 


45 "2 


1863 


30-4 


29 '5 


32-1 


29*0 


33-7 


3°"3 


33-1 


3*7 


36-5 


37'2 


41-7 


43-8 


417 


447 


1864 


27-1 


29'6 
29 '3 


23-3 


29 '5 
287 


28-3 


30-8 
30 - 5 


34-7 


3 I- 9 
32-2 


37-1 


37 'i 
37'i 


41-6 


43 '5 
43 '3 


44-8 


44'3 

44'3 


1865 


26 4 




25-6 




27-5 




32-9 




38-5 




43-0 




44-2 




1866 


31-2 


29 '0 


27-6 


28-4 


277 


30 -2 


32-3 


32 '3 


32-7 


37 '3 


43-0 


43 '3 


45-3 


44 \3 


1867 


22-3 


29'2 


32-3 


28-3 


25-9 


29 '9 


36-0 


3 2 '3 


37-8 


36-8 


427 


43 '2 


43-9 


44 '4 


1868 


28-3 


28'6 


32-4 


287 


32-1 


29"6 


34-6 


32-6 


387 


36'9 


42-5 


43 '2 


45-8 


44'4 


1869 


33 


28-6 
28-9 


32-7 


29 - o 
29'3 


27-2 


29-8 
29*6 


33-4 


32-8 
32-8 


32-3 


37 "o 

3 6 '7 


40 3 


43'* 

429 


46-1 


44'5 
44 -6 


1870 


28-0 




25-4 




28-1 




33-9 




38-5 




43-0 




47'5 




1871 


25-2 


28-8 


33-3 


29 'O 


32-0 


29 "4 


31-9 


3 2 '9 


36-5 


36-8 


40-7 


42-9 


44-8 


44-8 


1872 


29-6 


28-6 


32-0 


29'3 


31-6 


29-6 


33-7 


32-8 


34-6 


36-8 


42-1 


427 


457 


44-8 


1873 


30-5 


287 


25-4 


29 "4 


29-8 


29-8 


32-1 


3 2 "9 


33-8 


367 


42-4 


427 


45-5 


44"9 


1874 


31-0 


28-8 
28-9 


28-2 


29*2 

29 - I 


32-5 


29-8 
29 '9 


33 7 


32-9 
32 "9 


34-1 


36-S 
3 6- 4 


38-8 


427 
42-5 


45-6 


44"9 

44'9 


1875 


30-3 




26-9 




29-6 




313 




37-5 




39-7 




42-2 




1876 


29-7 


29 - o 


271 


29 'O 


28-2 


29-9 


32-6 


32-8 


35-1 


3 6 '4 


41-4 


42 '3 


45-3 


44-8 


1877 


28-5 


29 "O 


30-5 


28-9 


27-8 


29-8 


31-2 


32-8 


337 


36-4 


42-5 


42 '3 


45-8 


44-8 


1878 


28-4 


29 - o 


32-5 


29 - o 


29-1 


297 


33-9 


327 


37-3 


36-2 


41-9 


42-3 


46-1 


44 '9 


1879 


20-4 


28-9 
28-6 


25-5 


29 - 2 
29 'O 


28-1 


297 
29-6 


30-0 


32-8 
327 


32-2 


36-3 
36-1 


41-5 


42 '3 
42 - 3 


44-4 


44 "9 
44"9 


1880 


26-5 




31-5 




28-6 




31 '8 




34-4 




397 




437 




1881 


17-1 


28-5 


26-5 


29"I 


271 


29 '6 


29-3 


32-6 


36-0 


36-0 


39-4 


42 - 2 


45-3 


44'9 


1882 


32-7 


28-0 


32-9 


29 - o 


33 


29"S 


31-1 


32-5 


34-8 


36-0 


41-0 


42 - o 


45 5 


44 - 9 


1883 


30'2 


28-2 


31-8 


29 - 2 


26-0 


29-6 


32-9 


32 '4 


35-2 


35 "9 


41-3 


42'o 


45-0 


44'9 


1884 


32 3 


28-3 
28-4 


305 


29'3 
29 '3 


31-3 


29 '5 
29'5 


31-4 


32 '5 
3 2 '4 


36-5 


35 '9 
36-0 


42-0 


42 'O 
42 - o 


45-8 


44 '9 
44'9 


1885 


27-2 




28-6 




28-0 




32-5 




34-0 




40-7 




44-3 




1886 


24-8 


28-4 


25-7 


29"3 


28-3 


29 "5 


31-3 


3 2- 4 


36-0 


35 '9 


407 


41 '9 


447 


44'9 


1887 


29 5 


28-3 
28-3 


30-0 


29'2 
29'2 


27-7 


29-4 
29 '4 


29 '9 


3 2 '4 
32-3 


36-4 


35 '9 
35'9 


43-5 


41 '9 
41-9 


46-2 


44'9 
44"9 



MEAN SCOTTISH METEOROLOGY. 



199 



Table VI. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean op Black Bulb during Night. 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 

Quantities in 

eacli Year. 


Means of the 

Accumulating 

Years. 


Year 

repeated. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


°F. 


°F. 


T. 


°F. 


°F. 


°F. 


C F. 


°F. 


°F. 


°F. 


F. 


°F. 


1856 


477 




437 




39 3 




34 2 




36 1 




38-0 




1857 


43-5 




4M 




33-8 




29-3 




31-0 




35-1 




1858 


447 


45 - 6 
45 "3 


38-4 


42'4 
41M 


35-0 


36-6 
36-0 


27-8 


3 r8 
3° '4 


24-3 


33 -6 
3° "5 


34-6 


3 6'6 
35'9 


1859 


42-4 




38 




35-2 




30 -5 




26-0 




33-8 




1860 


47-0 


44 '6 


43-1 


40 '3 


38-5 


35-8 


28-8 


3°'4 


28-8 


29-4 


36-5 


35 '4 


1861 


44-9 


45 "i 


411 


4° '9 


356 


3 6 "4 


27-2 


30-1 


33-6 


29 - 2 


35-9 


35'6 


1862 


43-1 


45 'o 


38-5 


40-9 


36-6 


36-2 


33-6 


29-6 


31-3 


3°'° 


36-0 


35 '6 


1863 


41-1 


44-8 
44"3 


40-2 


40 '6 

40'5 


35-0 


36-3 
36-1 


so-o 


3°' 2 

30 '2 


31-6 


3° '2 
3° '3 


34-6 


357 
35 '6 


1864 


437 




45-4 




337 




30-3 




34 '3 




35-5 




1865 


43-5 


44'2 


397 


41-1 


38-5 


35 "9 


30-8 


30-2 


30-9 


30-8 


35-3 


35'6 


1866 


45-3 


44' 2 


41-6 


4°'9 


35-4 


36-1 


31-0 


3°' 2 


30-1 


30-8 


35-4 


35 '5 


1867 


45-9 


44'3 


41-4 


41 '0 


32-8 


36-1 


29-4 


3° '3 


31-9 


3° 7 


36-3 


35'5 


1868 


42-4 


44 '4 

44'2 


40-8 


41 - o 
41 'o 


36-2 


35-8 
35-8 


29-8 


30 -2 
30 -2 


25-0 


30-8 
3° '4 


34-9 


35 '6 

35 '5 


1869 


43-8 




40-2 




34-2 




287 




24-0 




34-6 




1870 


44-9 


44'2 


39 3 


40-9 


35-2 


357 


28 


30-I 


27-0 


29 '9 


34-9 


35 '5 


1871 


427 


44 '3 


39-4 


40-8 


33 6 


357 


313 


30-0 


29-3 


297 


35-5 


35 '4 


1872 


44-2 


44'2 


38-5 


407 


33-1 


35 '5 


31-0 


30-0 


33-1 


297 


35 


35 '4 


1873 


43-6 


44"2 
44-1 


40-9 


40 "6 
40 6 


33 6 


35 '4 
35 "o 


31-0 


3°'i 

3°'2 


20-0 


29 '9 
29 '4 


34-4 


35 '4 
35 "4 


1874 


45-8 




41-4 




37-1 




29-1 




29-2 




35-0 




1875 


44-2 


44"2 


41-1 


407 


40-4 


35 '4 


31-2 


30-1 


32-3 


29"3 


357 


35 '3 


1876 


44-5 


44'2 


37-5 


407 


357 


35 '6 


32-6 


30-2 


29-9 


29 '5 


35-0 


35 "4 


1877 


46-4 


44-2 


42-8 


40-5 


38-5 


35 '6 


27-4 


3°'3 


197 


29 '5 


35-3 


35 '3 


1878 


44-5 


44'3 
44'3 


39-4 


40 - 6 
40 '6 


33 4 


35'8 
357 


29-2 


30-1 
30-1 


23-1 


29'! 
28-8 


32-6 


35 '3 
35 '2 


1879 


45 2 




407 




29-1 




27-3 




27-5 




33-8 




1880 


40-6 


44"4 


40-8 


40 - 6 


33-1 


35 '4 


34-4 


30-0 


297 


287 


33-2 


35'2 


1881 


44-5 


44 '2 


39-2 


40 '6 


37-5 


35 - 3 


28-5 


3° '2 


24-5 


28-8 


35-4 


35"i 


1882 


44-3 


44 - 2 


417 


4° '5 


35-5 


35 '4 


31-0 


3° "i 


30-8 


28-6 


35-5 


35"i 


1883 


45-5 


44'2 
44"3 


42 '0 


40 '6 
40*6 


35-4 


35 '4 
35 '4 


29-2 


30-1 
30-1 


277 


287 
28-6 


35-8 


35'i 
35'i | 


1884 


41-3 




38-2 




32-2 




31-0 




29-1 




33-9 




1885 


45-3 


44-2 


407 


40 '6 


397 


35'3 


33 4 


30-1 


23-8 


28-6 


34-5 


35 - i 


1886 


43-9 


44'2 
44 '2 


39-8 


4<r6 
40 '5 


327 


35'4 
35 '3 


30-2 


3°' 2 

30 -2 


26-4 


28-5 
28-4 


347 


3S-i 
35 - i 


1887 



•200 



PROFESSOR C. PIAZZI SMYTH ON 



Table VII.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Humidity. 



Year. 


January. 


February, 


March. 


April. 


May. 


June. 


July. 


August. 


September 


October. 


November. 


December. 


VIean Month 

of Observed 

Quantities 

in each 


Successive 
Means of 

the Accu- 
mulating 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


(Hi. 


Ac. 


lib. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 






Sin. 




Mn. 




Mn. 




Mn. 




Mn. 




Mil. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 


Year. 


Years. 


1856 


85 




84 




79 




79 




77 




76 




77 




81 




83 




90 




89 




89 




82 




1857 


87 


86 


89 


86 


86 


82 


84 


82 


80 


78 


81 


78 


80 


78 


85 


83 


87 


8S 


90 


90 


90 


90 


88 


88 


86 


84 


1858 


86 


86 


83 


85 


85 


83 


78 


80 


81 


7" 


78 


78 


83 


80 


81 


82 


84 


85 


87 


89 


89 


89 


90 


89 


84 


84 


1859 


87 


86 


88 


86 


$:> 


84 


80 


80 


73 


78 


78 


78 


81 


80 


80 


82 


82 


84 


89 


89 


89 


89 


88 


89 


83 


84 


1860 


89 


87 


85 


86 


86 


84 


82 


81 


81 


78 


85 


So 


33 


80 


85 


82 


87 


85 


87 


89 


90 


89 


90 


89 


86 


84 


1861 


90 


87 


88 


86 


86 


84 


83 


81 


80 


79 


84 


80 


84 


81 


86 


83 


88 


8S 


90 


89 


87 


89 


90 


89 


86 


84 


1862 


90 


88 


89 


87 


88 


85 


83 


81 


84 


79 


83 


Si 


83 


82 


87 


84 


88 


86 


88 


89 


90 


89 


89 


89 


87 


85 


1863 


90 


88 


88 


87 


85 


85 


84 


82 


83 


So 


84 


81 


80 


81 


85 


84 


86 


86 


89 


89 


89 


89 


88 


89 


86 


85 


1864 


89 


88 


86 


87 


87 


35 


84 


82 


81 


80 


82 


81 


83 


82 


81 


83 


86 


86 


89 


89 


91 


89 


89 


89 


86 


85 


1865 


87 


88 


88 


87 


85 


85 


83 


82 


83 


80 


81 


81 


82 


82 


87 


84 


86 


86 


88 


89 


89 


89 


87 


89 


86 


85 


1866 


89 


88 


87 


87 


88 


8.S 


84 


82 


77 


80 


82 


81 


83 


82 


86 


84 


87 


86 


90 


89 


87 


89 


89 


89 


86 


85 


1867 


86 


88 


88 


87 


88 


36 


86 


82 


84 


So 


82 


81 


84 


82 


86 


84 


87 


86 


89 


89 


87 


89 


89 


89 


86 


8S 


1868 


89 


88 


86 


87 


85 


85 


84 


83 


80 


80 


77 


8! 


78 


82 


83 


84 


86 


86 


87 


89 


87 


89 


90 


89 


84 


85 


1869 


90 


88 


88 


87 


84 


35 


S2 


83 


78 


80 


80 


81 


82 


82 


82 


84 


86 


86 


88 


89 


87 


89 


88 


89 


85 


85 


1870 


89 


88 


88 


87 


87 


86 


81 


82 


82 


80 


83 


St 


83 


82 


82 


84 


87 


86 


88 


89 


89 


89 


87 


89 


86 


85 


1871 


88 


88 


89 


87 


84 


85 


85 


83 


79 


So 


81 


Si 


83 


82 


84 


84 


86 


86 


89 


89 


88 


89 


89 


89 


85 


85 


1872 


90 


88 


90 


87 


87 


85 


83 


83 


84 


80 


85 


81 


84 


82 


86 


84 


87 


86 


88 


89 


90 


89 


90 


89 


87 


85 


1873 


89 


88 


86 


87 


88 


86 


82 


83 


81 


80 


82 


81 


84 


82 


86 


84 


85 


86 


88 


88 


89 


89 


88 


89 


86 


85 


1874 


88 


88 


88 


87 


86 


86 


83 


83 


81 


80 


78 


Si 


82 


82 


84 


84 


86 


86 


87 


88 


89 


89 


84 


89 


85 


85 


1875 


92 


88 


88 


87 


85 


B6 


81 


83 


81 


80 


81 


81 


82 


82 


86 


84 


87 


86 


88 


88 


89 


89 


90 


89 


86 


85 


1876 


90 


89 


89 


87 


88 


86 


85 


83 


79 


So 


78 


81 


80 


82 


81 


84 


87 


86 


88 


88 


90 


89 


91 


89 


86 


85 


1877 


89 


89 


88 


87 


87 


86 


83 


83 


80 


80 


80 


81 


84 


82 


88 


84 


86 


86 


88 


88 


88 


89 


90 


89 


86 


85 


1878 


90 


89 


90 


88 


84 


86 


86 


83 


83 


80 


80 


81 


82 


82 


86 


84 


86 


86 


88 


88 


88 


89 


88 


89 


86 


85 


1879 


86 


89 


90 


88 


88 


86 


85 


83 


81 


81 


86 


81 


85 


82 


86 


84 


86 


86 


88 


88 


86 


89 


88 


89 


86 


85 


1880 


88 


89 


89 


88 


86 


86 


81 


83 


78 


80 


80 


81 


84 


82 


85 


84 


86 


86 


85 


88 


88 


89 


88 


89 


85 


85 


1881 


85 


88 


88 


88 


86 


86 


81 


83 


78 


80 


79 


81 


83 


82 


83 


84 


88 


86 


86 


88 


88 


89 


89 


89 


85 


85 


1882 


88 


88 


88 


88 


85 


86 


83 


83 


78 


80 


82 


Si 


84 


82 


84 


84 


87 


86 


90 


88 


88 


89 


89 


89 


86 


85 


1883 


88 


88 


88 


88 


85 


86 


82 


83 


80 


80 


80 


Si 


83 


82 


84 


84 


87 


86 


88 


88 


89 


89 


89 


89 


85 


85 


1884 


89 


88 


87 


88 


86 


86 


82 


83 


81 


80 


80 


81 


85 


82 


83 


84 


87 


86 


87 


88 


87 


89 


88 


89 


85 


85 


1885 


88 




89 




84 




82 




81 




78 




81 




83 




84 




85 




88 




89 




84 








88 




88 




86 




83 




80 


81 




82 




84 




86 




88 




89 




89 




85 


1886 


87 




88 




87 




si 




81 




78 




80 




83 




84 




89 




88 




86 




84 








88 




88 




86 




83 




80 




Si 




82 




84 




86 




88 


89 




89 




85 


1887 


87 




85 




85 




80 




77 




77 




78 




79 




85 




83 




87 




86 




82 








88 




88 




86 


|8 3 




80 




Si 




82 




84 




86 




88 




88 




89 




85 



MEAN SCOTTISH METEOROLOGY. 



201 



Table VIIL— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Number of Days on which Rain Fell. 





January. 


February. 


March. 


April. 


May. 


June. 


July. 


August. 


Septembei 


October. 


November. 


December. 


Mean Month 


Successive 


Year. 


























of Observed 

Quantities 

in each 

Year. 


Means of 
the Accu- 
mulating 
Years. 


Ob. 


' Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac 
Mn 


Ob. 


Ac 
Mn 


Ob. 


Ac 

Mn 


Ob. 


Ac 

Mn 


Ob, 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 

Mn. 


1856 


13 




13 




4 




12 




13 




18 




15 




14 




17 




12 




13 




16 




13 




1857 


16 


14 


11 


12 


16 


10 


16 


'4 


13 


13 


9 


14 


15 


IS 


10 


12 


15 


16 


16 


14 


12 


12 


14 


15 


14 


14 


1858 


14 


14 


6 


10 


13 


II 


g 


12 


16 


14 


12 


13 


17 


16 


15 


13 


14 


IS 


18 


15 


10 


12 


17 


16 


13 


13 


1859 


17 


IS 


17 


12 


11 


11 


15 


13 


4 


12 


11 


12 


14 


15 


14 


13 


17 


16 


14 


IS 


14 


12 


15 


16 


14 


14 


1860 


18 


16 


13 


12 


19 


13 


10 


12 


15 


12 


18 


14 


11 


14 


19 


14 


14 


IS 


22 


16 


17 


13 


17 


16 


16 


14 


1861 


14 


iS 


15 


12 


22 


14 


9 


12 


14 


12 


13 


14 


20 


>5 


22 


16 


19 


16 


14 


16 


19 


14 


13 


IS 


16 


14 


1862 


21 


16 


11 


12 


16 


14 


14 


12 


16 


13 


20 


14 


22 


16 


16 


16 


13 


16 


19 


16 


10 


14 


21 


16 


17 


15 


1863 


21 


17 


14 


12 


15 


14 


17 


13 


15 


*3 


18 


iS 


8 


15 


19 


16 


21 


16 


19 


17 


15 


14 


18 


16 


17 


iS 


1864 


14 


16 


14 


13 


16 


is 


12 


13 


12 


13 


17 


IS 


11 


'5 


13 


16 


19 


17 


13 


16 


16 


14 


17 


16 


14 


is 


1865 


17 


16 


14 


13 


15 


IS 


8 


12 


16 


13 


7 


14 


14 


IS 


18 


16 


7 


16 


14 


16 


15 


14 


15 


16 


13 


15 


1866 


19 


17 


19 


13 


16 


is 


13 


12 


10 


13 


12 


14 


13 


14 


19 


16 


19 


16 


13 


16 


16 


14 


20 


17 


16 


IS 


1867 


18 


17 


16 


14 


14 


IS 


20 


13 


14 


13 


12 


14 


14 


'4 


15 


16 


16 


16 


18 


16 


9 


14 


16 


17 


15 


iS 


1868 


17 


17 


18 


14 


17 


15 


13 


13 


15 


13 


11 


14 


6 


14 


16 


16 


13 


16 


17 


16 


13 


14 


19 


17 


15 


15 


1869 


18 


17 


19 


14 


12 


IS 


11 


13 


11 


13 


9 


13 


12 


14 


10 


16 


20 


16 


15 


16 


18 


14 


15 


17 


14 


15 


1870 


12 


17 


15 


14 


10 


14 


11 


13 


13 


13 


14 


13 


10 


14 


9 


15 


12 


16 


16 


16 


12 


14 


13 


16 


12 


IS 


1871 


13 


16 


16 


14 


13 


T 4 


16 


1-3 


9 


13 


11 


13 


20 


14 


11 


15 


12 


16 


17 


16 


14 


14 


17 


16 


14 


IS 


1872 


20 


17 


18 


IS 


17 


14 


14 


13 


19 


13 


20 


14 


13 


14 


16 


15 


22 


16 


19 


16 


21 


14 


18 


17 


18 


IS 


1873 


20 


17 


9 


14 


15 


14 


10 


13 


15 


13 


13 


'4 


21 


'4 


19 


15 


18 


16 


17 


16 


15 


14 


16 


16 


16 


IS 


1874 


18 


17 


11 


14 


16 


*s 


13 


13 


12 


13 


9 


■3 


14 


14 


20 


16 


19 


16 


17 


16 


17 


iS 


13 


16 


15 


15 


1875 


22 


18 


11 


14 


10 


iS 


8 


13 


14 


14 


17 


14 


12 


T5 


17 


16 


13 


16 


21 


17 


18 


15 


16 


17 


15 


iS 


1876 


15 


17 


18 


14 


21 


iS 


15 


13 


8 


13 


11 


13 


14 


14 


13 


15 


17 


16 


17 


17 


15 


15 


22 


17 


16 


15 


1877 


23 


17 


18 


14 


18 


is 


12 


13 


13 


13 


15 


14 


22 


14 


22 


16 


11 


16 


19 


17 


21 


IS 


18 


17 


18 


15 


1878 


16 


17 


12 


14 


13 


15 


10 


13 


17 


■3 


10 


13 


9 


14 


16 


16 


17 


16 


17 


17 


16 


IS 


14 


17 


14 


IS 


1879 


11 


17 


15 


14 


16 


J5 


12 


13 


14 


T 3 


18 


14 


19 


1 1 .' 


19 


16 


16 


16 


13 


17 


13 


15 


11 


16 


15 


IS 


1880 


10 


17 


18 


14 


9 


is 


18 


13 


10 


13 


13 


14 


16 


14 : 


6 


16 


15 


16 


13 


16 


17 


IS 


18 


16 


14 


IS 


1881 


9 


16 


15 


14 


16 


T 5 


10 


13 


12 


'3 


15 


14 


19 


15 


17 


16 


14 


16 


15 


16 


20 


IS 


15 


16 


15 


IS 


1882 


15 


16 


14 


14 


20 


IS 


14 


13 


12 


13 


17 


14 


22 


15 


14 


16 


16 


16 


18 


16 


20 


iS 


17 


16 


17 


IS 


1883 


17 


16 


17 


is 


14 


15 


10 


13 


13 


13 


12 


14 


15 


15 


15 


16 


15 


16 


16 


16 


18 


16 


17 


16 


15 


iS 


1884 


20 


16 


15 


15 


15 


15 


12 


13 


14 


1 5 


9 


13 


19 


15 


12 


15 


15 


16 


16 


16 


14 


IS 


17 


16 


15 


15 


1885 


15 


16 


18 


iS 


13 


15 


11 


12 


20 


13 


11 


13 


11 


15 


10 


IS 


19 


16 


18 


16 


14 


15 


14 


16 


14 


IS 


1886 


20 




14 




17 




13 




16 




10 




15 




14 


15 




19 




18 




17 




16 








17 




is 




15 




13 




13 




1 3 




75 




15 




16 




17 




15 




16 




15 


1887 


16 




12 




13 




11 




10 




7 




18 




14 




17 




13 




17 




16 




14 








17 




15 


15 




"1 


13 




15 




'5 




IS 




16 




16 




16 




16 




IS 



VOL. XXXV. PART 3. 



2 F 



202 



PROFESSOR C. PIAZZI SMYTH ON 



Table IX.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Depth of Rain in Inches. 





January. 


Fcbniavy. 


March. 


April. 


May. 


June. 


July. 




Obsd. 


Accumg. 

Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg. 
Means. 


1856 


238 




3-30 




0-26 




2-44 




2-62 




371 




2-55 




1857 


2-77 




1-54 




2-94 




2-38 




1-66 




2-79 




2-17 




1858 


2-98 


2- 5 8 


1-13 


2 '42 


1-95 


i - 6o 


1-86 


2-41 


2-81 


2 "14 


2 -36 


3' 2 S 


4-31 


2-36 


1859 


4-21 


271 

3-08 


3-38 


1 '99 
2 '34 


4-18 


172 

2 '33 


3-20 


2-23 
2 '47 


0-29 


2-36 
1-84 


2-04 


2'9S 
272 


2-76 


3 '01 

2 '95 


1860 


4 56 




2-69 




3-52 




1-18 




2-18 




4-34 




1-82 




1861 


3 09 


3-38 


3 32 


2 - 4I 


5-10 


2 '57 


1-04 


2"2I 


1-57 


I-9I 


2-35 


3'°5 


3-94 


272 


1862 


5-32 


3'33 


1-88 


2-56 


3-63 


2 '99 


2-99 


2 - 02 


3-89 


1-86 


3-99 


2 '93 


3-87 


2 '92 


1863 


6-20 


3-62 


2-40 


2 "46 


2-08 


3-08 


3-27 


2 - l6 


2-34 


2'IS 


3 24 


3 -08 


0-72 


3-06 


1864 


2-84 


3 '94 
3-82 


375 


2 "46 
2 - 6o 


3-96 


2 "96 

3'°7 


1-57 


2-30 
2'2I 


1-98 


2'17 

2-15 


2-57 


3-10 
3'°4 


2-37 


277 
272 


1865 


3-73 




2-91 




2-05 




0'94 




3-36 




0-75 




3-09 




1866 


5-31 


3-8i 


4-51 


2-63 


315 


2 '97 


1-68 


2 '09 


1-36 


2*27 


1-85 


2'8l 


3-14 


276 


1867 


4-74 


3 '94 


3 09 


2-80 


2 '26 


2-98 


4-43 


2-05 


2-83 


2 - I9 


2-11 


2'73 


4-38 


279 


1868 


5-53 


4 - oi 


475 


2-82 


4-22 


2-92 


3-31 


2-25 


2-51 


2 '24 


1-14 


2-68 


0-70 


2 '93 


1869 


4-85 


4'i3 
4-18 


4 '05 


2 '97 
3'°5 


1-33 


3 -02 
2 - gO 


1-99 


2 '33 
2-31 


1-37 


2 - 26 
2'20 


2-15 


2-56 
2'53 


1-62 


276 

2 '67 


1870 


3-08 




3-89 




1-24 




1-58 




2-61 




1-91 




1-88 




1871 


2-74 


4'" 


4-40 


3'" 


2-50 


279 


4-08 


2 '26 


1-12 


2-23 


2-07 


2-49 


4-16 


2 "62 


1872 


6 '48 


4 '02 


4-28 


3'i9 


3 26 


277 


2-14 


2 '37 


3-32 


2"l6 


5-16 


2 "46 


3 '59 


272 


1873 


5-37 


4' 17 


1-45 


3 '25 


2-32 


2-80 


0-70 


2-36 


2-69 


2 - 22 


1-74 


2 "62 


4-57 


277 


1874 


4-02 


4'23 

4 - 22 


1-71 


3 -I 5 
3-08 


2-82 


278 
278 


2-27 


2 "27 
2 '27 


1-82 


2'25 
2-23 


1-42 


2 '57 

2'SI 


3-11 


2-87 
2-88 


1875 


5-63 




1-72 




1-68 




1-41 




2-03 




314 




2-90 




1876 


2-84 


4-29 


4-33 


3-01 


5-10 


272 


311 


2 - 22 


0-91 


2 '22 


3-12 


2 '54 


2-26 


2-88 


1877 


6-96 


4 '22 


4-12 


3'°7 


2-58 


2-84 


2-96 


2 "27 


2-75 


2"l6 


3-72 


2 '57 


4-31 


2-85 


1878 


4-01 


4'3S 


1-92 


3'i2 


2-09 


2-82 


171 


2-30 


3-39 


2-18 


2-78 


2'62 


1-12 


2 '92 


1879 


1-84 


4 '33 
4'23 


2-52 


3'°7 
3'°4 


3-20 


2'79 

2-81 


1-89 


2 "27 
2 '26 


2-30 


2 "24 
2 '24 


4-24 


2-63 
2^69 


5-03 


2-84 
2 '93 


1880 


2-02 




3-98 




2-32 




3-37 




1-20 




2-09 




3-69 




1881 


1-30 


4-14 


3-79 


3-08 


3-49 


279 


1-16 


2- 3 


2-48 


2'20 


3-23 


2 '6j 


4-16 


2 "96 


1882 


341 


4 '03 


3-20 


3' 11 


4-17 


2-82 


3-09 


2 - 26 


2-16 


2"2I 


3-68 


2 '69 


4-67 


301 


1883 


4-48 


4'oi 


4-14 


3'n 


2-36 


2-87 


1-88 


2 - 29 


1-84 


2'2I 


2-34 


2 73 


3-78 


3 '°7 


1884 


5-80 


4"02 

4-09 


3-84 


3'iS 
3'i7 


3-24 


2-85 

2-86 


1-31 


2 '27 
2 '24 


3 01 


2 - I9 
2 '22 


0-87 


272 
2-65 


4-74 


3-10 
3'i5 


1885 


2-93 




4-35 




2-53 




2-56 




3-22 




1-45 




1-65 




1886 


4-42 


4 '°S 


1-81 


3'2I 


314 


285 


1-98 


2-25 


3-57 


2-25 


1-58 


2 '6l 


3-39 


3-10 


1887 


3-25 


4'o6 
4 '°3 


2-46 


3'i7 
3 "H 


1-88 


2-86 
2-83 


2-05 


2*24 
2 "24 


1-39 


2-30 
2 - 27 


0-96 


2'58 
2 '53 


2-97 


3" 
3' 11 



MEAN SCOTTISH METEOROLOGY. 



203 



Table IX. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Depth of Rain in Inches. 

























Successiv 




Successive 




August. 


September. 


October. 


November. 


December. 


Mean Month 

of Observed 

Quantities 

in each 

Year. 


Means of 

Mean 
Months 
the Accu- 
mulating 
Years. 


Yearly 

Sums of 

Observed 

Quantities. 


Means of 
Sums of 
the Accu- 
mulating 
Years. 


Year 
repeated. 


Obsd. 


Accumg. 
Means. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


3-46 




4-64 




1-43 




2-12 




4-09 




275 




33-00 




1856 


1-87 




3-82 




2-36 




2-89 




3-37 




2-55 




30-56 




1857 


2-61 


266 


2-80 


4' 23 


4-72 


1-89 


2-38 


2-50 


4-00 


373 


2-83 


2-65 


33-91 


3178 


1858 


2-27 


2 -65 
2'S5 


3 21 


375 
3-62 


4-60 


2-84 
3-28 


3 37 


2 "46 
2-69 


3-66 


3 '82 
378 


3-10 


2'7I 
2"8l 


37-17 


32-49 
33 "66 


1859 


379 




1-92 




5-14 




2-83 




3-91 




3-16 




37-88 




1860 


6-44 


2-8o 


5-27 


3 '28 


3-34 


3'65 


6-63 


272 


2-98 


3'8i 


376 


2-88 


45-07 


34 - 5° 


1861 


3 35 


3 '4i 


2-44 


3'6i 


6-32 


3-60 


2-41 


3 '37 


5-20 


3 '67 


377 


3 '02 


45-29 


36-26 


1862 


4-50 


3 '4° 


4-72 


3 '44 


411 


3 '99 


3-52 


323 


5-01 


3-89 


3-51 


3'i3 


42-11 


37 "55 


1863 


1-66 


3 '54 
3 '33 


4-61 


3-60 
37i 


5-47 


4'oo 

4'i7 


4-09 


3 '27 
3 '36 


371 


4 '°3 
3 '99 


3'22 


3'i8 
3'i8 


38-58 


38-12 

38'i7 


1864 


3-89 




1-14 




5-11 




3-29 




3-65 




2-83 




33-91 




1865 


3-99 


3'38 


4-34 


3 '46 


2-86 


4 '26 


3 93 


3 '35 


5-29 


3 '96 


3-45 


3'iS 


41-41 


3775 


1866 


2-82 


3'44 


317 


3 '53 


4-29 


4'i3 


1-25 


3 '4i 


3-15 


4-08 


3 21 


3'i8 


38-52 


38-08 


1867 


5-18 


3 '39 


3-34 


3'5i 


3-71 


4'i5 


2-62 


3 '23 


6-02 


4'oo 


3-59 


3'i8 


43-03 


38-12 


1868 


1-32 


3 '52 
3 '37 


5-92 


3 '5° 
3 '69 


3-00 


4-11 
4 '03 


4-28 


3'i8 
3 '26 


4-66 


4 - i6 
4'ig 


3-04 


3-21 
3 '20 


36-54 


38'50 
38-35 


1869 


1-55 




3-32 




4-63 




2 58 




3-54 




2-65 




31-81 




1870 


2 92 


3' 2 5 


2-57 


3 '64 


3-46 


4-07 


3-41 


3 '21 


376 


4 - i5 


3-10 


3-16 


37-19 


37^2 


1871 


3-89 


3 '23 


5-94 


3-58 


475 


4 '°3 


6-01 


3 "22 


5-33 


4 - I2 


4'51 


3-16 


54-15 


37-87 


1872 


4-21 


3 '27 


4-36 


372 


5-47 


4-08 


3-32 


3 '39 


3-13 


4'20 


3-28 


3 '24 


39-33 


38-83 


1873 


5-54 


3 '32 
3 '43 


4-18 


375 
377 


6-05 


4'i5 
4 '26 


4-54 


3'38 
3 '44 


2-69 


4-14 

4 '06 


3-35 


3 '24 
3 '25 


40-17 


38-86 
38-93 


1874 


2-97 




4-34 




472 




4-87 




3-67 




3-26 




39-08 




1875 


373 


3 '4i 


3-56 


3'8o 


477 


4-28 


3-58 


3 '52 


7-57 


4-04 


374 


3' 2 5 


44-88 


38-94 


1876 


6 35 


3 '43 


2-12 


379 


5-32 


4'3° 


6-07 


3 '52 


4-57 


4'2I 


4-32 


3'27 


51-83 


39-22 


1877 


3 96 


3 '56 


4-62 


37i 


4-46 


4 '35 


3 21 


3 '64 


3-01 


4 "23 


3-02 


3 '32 


36-28 


3979 


1878 


4-48 


3'58 
3-61 


3-99 


375 
376 


1-97 


4 '35 
4 - 25 


2-27 


3 '62 
3 '56 


270 


4'i7 
4-11 


304 


3 '3° 
3 '29 


36-43 


39-64 
39-5I 


1879 


86 




3-68 




2-53 




5/03 




3-96 




2-89 




34-73 




1880 


4-33 


3 '5° 


3-01 


376 


3 51 


4-18 


5-21 


3-62 


3-87 


4'" 


3-30 


3-28 


39-54 


39-31 


1881 


2-71 


3 '54 


3-63 


373 


3-62 


4-16 


5-42 


3-68 


5-16 


4'io 


374 


3'28 


44-92 


39-32 


1882 


4-11 


3 'Si 


3-26 


373 


4-04 


4-14 


4-59 


375 


3-56 


4-14 


3-36 


3 "29 


40-38 


39-53 


1883 


2-47 


3 '53 
3 "49 


2-72 


37i 
3-68 


3 46 


4'i3 
4-11 


3-40 


378 
376 


4-58 


4'12 

4 -I 3 


3 '29 


3 '3° 
3 '3° 


39-44 


39-56 
39-56 


1884 


2-70 




5-32 




3-28 




2-54 




2-89 




2-95 




35-42 




1885 


2-06 


3 '46 


3-96 


373 


3 99 


4*08 


3-87 


372 


4-16 


4 '°9 


3-16 


3 " 2 9 


37-93 


39-42 


1886 


272 


3 '42 


3-83 


374 


2-39 


4-08 


376 


373 


3-30 


4-09 


2-58 


3'28 


30-96 


39'37 

1 


1887 




3'4o 




374 




4 '03 




373 




4'°7 




326 




39-12 





204 



PROFESSOR C. PIAZZI SMYTH ON 



Table X.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Mean Force op the "Wind ; lbs. Avoir, on Square Foot. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


July. 


oi»a. 


Accumg. 


Obsd. 


Accumg. 


Obsd. 


Accumg. 


Obsd. 


Accumg. 


Obsd. 


Accumg. 


Obsd. 


Accumg. 


Obsd. 


Accumg. 






Means. 




Means. 




Means. 




Means. 




Means. 




Means. 




Means. 


1856 


1 •_'2 




2-20 




1-65 




0-98 




0-97 




1-90 




1-34 




1857 


1-25 


I '24 


1-77 


1-98 


1-88 


176 


1-18 


1-08 


0-79 


o-88 


0-65 


1-28 


1-55 


1 '44 


1858 


2 36 


i'6i 


1-80 


1 '92 


1-89 


i-8i 


1-45 


1 '20 


1-34 


1-03 


1-36 


1 '3° 


111 


1 '33 


1859 


2-95 


i '94 


2-67 


2 - II 


3-19 


2'i5 


2-33 


1*48 


0-84 


0-98 


1-66 


1 '39 


1-44 


1-36 


1860 


1-78 


r 9 i 


2-33 


2-15 


1-95 


2"II 


1-55 


1 '5° 


1-42 


1 '07 


1-28 


1 '37 


0'87 


1 "26 


1861 


1-33 


1-82 


2-22 


2 - l6 


2-64 


2"20 


1-13 


1 "44 


1-18 


1 "09 


0-88 


1 '29 


1-41 


i "29 


1862 


1-68 


r8o 


1-36 


2-05 


1-36 


2-08 


1-57 


1 "46 


1-27 


I/I2 


1-67 


1 '34 


1-76 


1 '35 


1863 


1-98 


1-82 


1-90 


2-03 


1-54 


2'OI 


1-87 


I 'S I 


114 


I '12 


1-05 


t'3 1 


1-03 


i"3* 


1864 


1-54 


1 79 


1-31 


1 '95 


1-47 


i"95 


1-02 


1 '45 


1-13 


I '12 


1-46 


1 '32 


115 


1 '3° 


1865 


1-97 


i-8i 


1-28 


r88 


1-62 


1 '92 


1-22 


1 '43 


1-48 


ri6 


111 


1-30 


0-98 


1 '26 


1866 


2-18 


1-84 


1-89 


r88 


1-48 


i-88 


1-54 


1 -44 


1-05 


I-I S 


0-86 


1 26 


0-90 


1 '23 


1867 


1-43 


i-8i 


2-13 


i'90 


1-63 


i-86 


1-84 


1 '47 


1-31 


ri6 


0-98 


1 "24 


1-04 


I '22 


1868 


1-92 


1-82 


3 21 


2'00 


2-13 


r88 


1-56 


1 '48 


1-49 


rig 


1-58 


1 "26 


0-94 


1-19 


1869 


1-83 


1-82 


2-05 


2"OI 


1-43 


i'8 S 


1-40 


1 '47 


1-44 


I "20 


1-08 


1 '25 


1-28 


I'20 


1870 


104 


1*76 


1-70 


1 '99 


1-31 


r8i 


1-66 


1-49 


1-47 


I "22 


112 


1 '24 


1-05 


1M9 


1871 


1-36 


T '74 


2'12 


2 - 00 


1-87 


1-82 


1-36 


1-48 


1-12 


I '22 


1-07 


1 '23 


111 


i-i8 


1872 


2-13 


176 


1-93 


i -99 


1-80 


i-8i 


2-14 


i'S 2 


1-59 


I '24 


118 


1 '23 


115 


ri8 


1873 


2-06 


178 


1-36 


1 '96 


1-30 


179 


1-47 


1 '5 2 


1-23 


I-2 4 


1-32 


1 '23 


1-09 


1-18 


1874 


2-24 


i-8o 


1-30 


1 '92 


2-30 


I -8! 


1-66 


1 '52 


1-32 


I "24 


1-51 


1 '25 


113 


1-18 


1875 


1-75 


i-8o 


1-39 


1*90 


1-46 


i-8o 


1-02 


1 '5° 


1-15 


I '24 


110 


1 '24 


1-09 


1-17 


1876 


2 37 


1 "83 


1-84 


1-89 


3-01 


1 -85 


1-97 


1 -52 


1-46 


I '25 


1-72 


1 '26 


2-07 


I'2I 


1877 


3 '01 


i-88 


2-97 


1 '94 


2-20 


I -87 


2-73 


r S 8 


2-37 


I -30 


2-03 


1 -30 


1-85 


I '24 


1878 


1-92 


i-88 


1-71 


1 '93 


2-42 


1-89 


1-59 


1-58 


1-81 


1-32 


1-27 


1-30 


1-27 


I '24 


1879 


1-74 


i-88 


1-68 


1 '92 


2-98 


1-94 


1-77 


i-S8 


1-68 


r 34 


1-35 


1-30 


2-00 


1-28 


1880 


1-82 


1 -87 


3-00 


1 '96 


1-39 


1 '92 


2-06 


i - 6o 


2-02 


1-36 


1-52 


1 '3i 


111 


I '27 


1881 


1-27 


I-8 5 


1-94 


1 "96 


2-87 


1 '95 


1-87 


i-6i 


1-90 


1-38 


2-01 


1 '34 


2-03 


I -30 


1882 


2-92 


1-89 


283 


i'99 


3-65 


2 "02 


2 -47 


1 '64 


1-63 


1 "39 


1-71 


1 '35 


1-49 


i'3i 


1883 


2-91 


1 '93 


3-99 


2*07 


2-99 


2-05 


2-16 


i-66 


2-53 


1 '43 


1-58 


1-36 


1-56 


i'3 J 


1884 


3-92 


2'00 


3-19 


2'H 


2-32 


2'C>6 


1-47 


i-66 


2-11 


1 '46 


1-59 


1 '37 


1-20 


i'3 T 


1885 


2-35 


2'OI 


2-70 


2T3 


2-89 


2 '09 


2-33 


i-68 


2-23 


1-48 


1-64 


1 '37 


1-35 


'"3 1 


1886 


2-99 


2 '04 


1-51 


2-II 


2-59 


2'10 


2-62 


171 


2-08 


1 'S° 


2-19 


1 "40 


2-23 


1 '34 


1887 


2-76 




238 




1-81 




1-96 




1-98 




1-37 




1-73 






! 


2 - o6 




2 - II 




2'09 




172 




1 52 




1 '40 




1 '35 



MEAN SCOTTISH METEOROLOGY. 



205 



Table X. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Force of the Wind ; lbs. Avoir, on Square Foot. 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 
Quantities in 
each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


Obsd. 


Accumg 
Means. 


1-01 




1-69 




0-88 




0-97 




1-87 




1-39 




1856 


1-04 




1-38 




1-29 




110 




2-32 




1-35 




1857 


0-99 


I'02 


1-68 


i '54 


1-90 


1-08 


1-09 


1 '04 


1-80 


2 - IO 


1-56 


1 '37 


1858 


1-58 


I'OI 

i-i6 


1-80 


i -58 
I "64 


1-63 


1-36 
1 "42 


1-31 


1 '°S 
I "12 


1-67 


2 "00 
I '92 


1-92 


1 '43 
i'56 


1859 


1-15 




1-09 




2-34 




1-09 




1-37 




1-52 




1860 


1-92 


iiS 


1-38 


1 'S3 


1-28 


r6i 


2-36 


I'll 


1-20 


i-8i 


1-58 


1 '55 


1861 


0-82 


1-28 


0-92 


1 'So 


2-07 


i'SS 


0-80 


I '32 


2-15 


170 


1-45 


1 '55 


1862 


1-14 


I "21 


1-69 


i '42 


1-46 


1 '63 


1-37 


I '25 


2 39 


I'77 


1-55 


1 '54 


1863 


1-09 


I'20 

i'i9 


1-50 


1 '45 
1 "46 


1-25 


i-6i 

1 "57 


1-13 


I 26 
I'2S 


1-31 


I'8 5 
I'79 


1-28 


1 '54 
i'Si 


1864 


0-88 




1-25 




173 




1-06 




2-50 




1-42 




1865 


1-16 


ri6 


1-36 


1 '44 


1-06 


1 -58 


1-78 


I '23 


1-80 


i-86 


1-42 


1 'So 


1866 


0-97 


n6 


1-46 


1 '43 


1-37 


1 "54 


1-03 


1-28 


1-60 


i'8 5 


1-40 


1 '49 


1867 


1-60. 


i '14 


1-21 


1 '43 


1-64 


1 '52 


1-37 


I '26 


1-69 


183 


170 


1 '49 


1868 


1-16 


ri8 
i-i8 


1-90 


1 "42 

1 '45 


1-62 


1 '53 

1 '54 


1-92 


I "27 
I '31 


1-85 


1-82 
1-82 


1-58 


1-50 
i'Si 


1869 


0-84 




1-13 




1-50 




1-04 




1-28 




1-26 




1870 


1-26 


i-i6 


1-04 


1 '43 


1-42 


1 '53 


1-36 


I "29 


1-64 


179 


1-39 


1 '49 


1871 


0-93 


i-i6 


1-52 


1 '40 


1-82 


1 '53 


1-92 


1 '3° 


1-90 


178 


1-67 


1 '49 


1872 


1-24 


i'iS 


1-34 


1 '4i 


1-31 


1 '54 


1-65 


1 '34 


1-96 


r 7 8 


1-44 


1 'So 


1873 


139 


ri6 
i '17 


1-65 


1-41 
1 "42 


1-81 


1 '53 

1 '55 


1-31 


1 '3° 
1 '35 


1-30 


i'74 
172 


1-58 


1 "49 
1 'So 


1874 


1-27 




1-24 




2-61 




1-56 




1-81 




1-45 




1875 


1-82 


i '17 


1-36 


1 '41 


2-03 


i'6o 


1-70 


1-36 


2-64 


i'77 


2-00 


1 'So 


1876 


1-46 


I - 20 


1-69 


1 '41 


2-69 


1 "62 


2-61 


1-38 


2-23 


i-8i 


2-32 


1 '52 


1877 


1-41 


I '21 


2-40 


1 '42 


2-85 


1 '67 


1-91 


1 '43 


1-39 


i'8 3 


1-83 


1 '56 


1878 


1-61 


I "22 

i '24 


2-04 


1 '46 

1 '49 


1-38 


172 
i'7i 


2-29 


1 '45 
1 '49 


2-03 


1 -8: 
1-82 


1-88 


1 '57 

r 5 8 | 


1879 


0-83 




1-47 




1-92 




2-82 




2-45 




1-87 




1880 


2-01 


I '22 


1-50 


1 '49 


3-37 


i'7i 


371 


1 '54 


2-45 


1-85 


2-24 


1 '59 | 


1881 


1-91 


I '25 


1-72 


1 '49 


2-07 


178 


2-73 


1 '63 


1-96 


1 '87 


2-26 


1 "62 


1882 


2-00 


1-28 


1-89 


i'S° 


2-47 


i'79 


2-43 


1 '°7 


2-57 


1-87 


2-42 


1 "64 


1883 


1-40 


i '3° 
i '3i 


1-91 


I'Si 

1 -52 


3 '03 


i-8i 
1 '86 


2-38 


1 '69 
172 


2-57 


1 '90 
1 "92 


2-26 


1 "67 

1*69 j 


1884 


1-70 




2-46 




2-47 




1-90 




2-85 




2-24 




1885 


1-70 


I '32 


1-99 


i'S6 


1-77 


i-88 


2-25 


172 


2-23 


1 '95 


2-18 


I'7I 


1886 


1-25 


i '33 
i '33 


1-75 


1 '57 
1-58 


2-24 


1-87 
i-88 


2-06 


i"74 
i'75 


2-08 


i "96 
1*96 


1-95 


172 

I'73 | 


1887 



VOL. XXXV. PART 3. 



2G 



•206 



PROFESSOR C. PIAZZI SMYTH ON 



Table XI.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Winds — Northern Quarter, | N.W., N, and | N.E. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


July. 


August. 


September 


October. 


November. 


December. 


Mean Month 

of Observed 

Quantities 

in each 

Year. 


Successive 
Means of 
the Accu- 
mulating 
Years. 


Ob. 


A 1 '- 
n. 


Ob. 
3 


Ac. 

Ma 


Ob. 

7 


Ac 

Mn. 


Ob. 
6 


Ac. 
Mn. 


0b. 

8 


Ac. 
Mil. 


Ob. 
3 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


1856 


7 




4 




6 




7 




2 




9 




8 




6 




1857 


7 




1 




4 




4 




4 




5 




4 




5 




4 




4 




5 




2 




1 




1858 


4 


7 


4 


2 


8 





4 


5 


5 


6 


2 


4 


5 


4 


4 


6 


2 


6 


6 


3 


6 


7 


2 


s 


4 


5 


1859 


3 


6 

5 


2 


3 

2 


5 




6 


8 





4 



5 


6 


3 

4 


3 


4 
4 


1 


5 

4 


1 


4 
4 


7 


4 
5 


5 


7 
6 


7 


4 
5 


4 


5 
4 


1860 


7 




9 




6 




8 




3 




4 




6 




4 




6 




4 




4 




7 




6 




1861 


4 


6 


4 


4 


4 


6 


6 


6 


8 


5 


6 


4 


3 


4 


2 


4 


5 


4 


2 


5 


7 


6 


6 


5 


5 


5 


1862 


4 


5 


4 


4 


6 


6 


6 





3 


5 


6 


4 


4 


4 


4 


4 


3 


4 


2 


"4 


4 


6 


3 


5 


4 


5 


1863 


4 


S 


2 


4 


4 





4 


6 


6 


5 


2 


5 


7 


4 


4 


4 


4 


4 


2 


4 


2 


6 


5 


5 


4 


5 


1864 


2 


5 
5 


6 


4 

4 


7 


6 
6 


4 


6 

6 


7 


5 
5 


4 


4 
4 


5 


4 

s 


8 


4 
4 


2 


4 
4 


6 


4 
4 


4 


S 
S 


3 


5 
5 


5 


S 
5 


1865 


8 




5 




8 




4 




4 




5 




4 




4 




2 




8 




6 




2 




5 




1866 


3 


5 


6 


4 


6 


6 


6 


5 


5 


5 


1 


4 


7 


4 


5 


4 


2 


4 


3 


4 


6 


S 


4 


4 


5 


5 


1867 


10 


5 


3 


4 


8 


6 


4 


6 


5 


5 


6 


4 


8 


5 


2 


4 


4 


3 


4 


4 


6 


5 


8 


4 


6 


5 


1868 


4 


S 


3 


4 


4 


6 


4 


5 


2 


5 


2 


4 


4 


5 


3 


4 


6 


4 


4 


4 


6 


S 


3 


S 


4 


s 


1869 


2 


S 
5 


3 


4 
4 


11 


6 

6 


4 


5 
5 


8 


5 
5 


8 


4 
4 


2 


5 

5 


6 


4 
4 


3 


4 
4 


8 


4 

4 


8 


5 
6 


8 


5 

5 


6 


5 
5 


1870 


4 




6 




8 




4 




6 




6 




4 




8 




4 




6 




8 




8 




6 




1871 


4 


5 


3 


4 


6 


6 


6 


S 


8 


5 


8 


S 


3 


S 


3 


4 


6 


4 


4 


4 


9 


6 


6 


5 


6 


S 


1872 


3 


5 


2 


4 


6 


6 


8 


5 


8 


5 


3 


5 


6 


5 


6 


4 


8 


4 


6 


4 


6 


6 


5 


5 


6 


5 


1873 


2 


5 


9 


4 


6 


6 


10 


s 


8 


6 


4 


S 


2 


5 


4 


4 


8 


4 


5 


S 


6 


6 


2 


5 


6 


5 


1874 


4 


5 
5 


2 


4 
4 


6 


6 
6 


3 


6 

5 


9 


6 
6 


6 


5 

5 


2 


4 
4 


4 


4 
4 


4 


4 
4 


4 


5 
5 


6 


6 
6 


12 


5 
5 


5 


S 
5 


1875 


2 




6 




6 




6 




4 




■2 




8 




4 




4 




2 




8 




6 




5 




1876 


4 


4 


6 


4 


8 


6 


6 


S 


7 


6 


4 


S 


4 


5 


4 


4 


8 


4 


3 


4 


6 


6 


3 


S 


5 


5 


1877 


4 


4 


6 


4 


7 


6 


5 


5 


7 


6 


2 


5 


3 


5 


6 


4 


8 


4 


4 


4 


2 


6 


4 


5 


5 


S 


1878 


6 


4 


2 


4 


10 


6 


4 


5 


5 


6 


4 


4 


6 


4 


5 


4 


4 


S 


5 


4 


13 


6 


12 


5 


6 


5 


1879 


4 


4 

4 


6 


4 
4 


4 


7 
6 


7 


5 

5 


8 


6 
6 


4 


4 
4 


6 


5 
5 


4 


4 
4 


3 


s 

5 


6 


4 
4 


11 


6 
6 


6 


5 
5 


6 


5 
S 


1880 


4 




2 




3 




6 




7 









6 




5 




4 




12 




6 




7 




6 




1881 


8 


4 


7 


4 


6 


6 


7 


5 


4 


6 


§ 


4 


3 


5 


7 


4 


5 


4 


6 


5 


2 


6 


4 


6 


5 


5 


1882 


3 


5 


3 


4 


4 


6 


5 


6 


5 


6 


6 


4 


3 


5 


6 


S 


5 


4 


4 


5 


6 


6 


6 


6 


5 


5 


1883 


3 


4 


3 


4 


12 


6 


3 


6 


7 


6 


g 


S 


8 


S 


3 


5 


6 


S 


6 


S 


5 


6 


7 


6 


6 


5 


1884 


3 


4 
4 


3 


4 

4 


3 


6 

6 


6 


5 
5 


3 




6 


5 


5 

5 


3 


5 
5 


3 


5 
4 


3 


5 
5 


6 


5 
5 


8 


6 
6 


4 


6 
6 


4 


S 

S 


1885 


5 




3 




8 




4 




8 




i; 




3 




8 




4 




9 




4 




6 




6 




1886 


8 


4 


4 


4 


4 


6 


7 


5 


5 


6 


r. 


5 


4 


S 


3 


5 


4 


5 


3 


S 


5 


6 


9 


6 


5 


s 


1887 


3 


5 

4 


4 


4 
4 


7 


6 
6 


8 


S 
6 


8 


6 
6 


i 


5 
5 


4 


S 
5 


6 


S 
S 


7 


4 

5 


10 


5 
S 


6 


6 
6 


8 


6 
6 


6 


5 

S 



MEAN SCOTTISH METEOROLOGY. 



207 



Table XII.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Winds — Eastern Quarter, £ N.E., E., and ^ S.E. 





Jan 


uary. 


February 


March. 


April. 


May. 


June. 


July.' 


August. 


September October. 


Novembei 


. December 


Mean Month Successive 


Year. 




























of Observed Means of 
















































Quantities 


MIC AUUU 






Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


()b 


Ac 

Mn 


Ob 


Ac 
Mn 


' Ob 


Ac 

• Mn 


• Ob 


Ac 

Mn 


'Ob 


Ac 
• Mn 


' Ob. 


Ac. 

Mn 


Ob 


Ac. 

Mn 


Ob. 


Ac. 

Mn 


Ob 


Ac. 

Mn. 


Ob 


Ac 
Mn 


in each 
Year. 


mulating 
Years. 




1856 


8 




6 




12 




10 




16 




4 




2 




9 




8 




6 




4 




2 




7 






1857 


4 


6 


2 


4 


10 


II 


10 


IO 


13 


r 4 


10 


7 


1 


2 


7 


83 


6 


7 


7 


6 


8 


6 





I 


6 


6 




1858 


2 


5 


9 


6 


3 


8 


8 


9 


6 


12 


4 


6 


4 


2 


4 


7 


4 


6 


4 


6 


8 


7 


3 


2 


5 


6 




1859 


1 


4 


2 


S 


2 


7 


8 


9 


10 


11 


8 


6 


6 


3 


1 


S 


4 


6 


8 


6 


4 


6 


5 


2 


5 


6 




1860 


7 


4 


2 


4 


3 


6 


8 


9 


8 


II 


10 


7 


6 


4 


5 


s 


4 


5 


2 


5 


12 


7 


9 


4 


6 


6 




1861 


5 


4 


5 


4 


2 


S 


8 


9 


5 


IO 


11 


8 


6 


4 


2 


s 


4 


5 


4 


5 


4 


7 


3 


4 


5 


6 




1862 


5 


5 


8 


5 


14 


7 


4 


8 


6 


9 


4 


7 


4 


4 


6 


s 


6 


S 


2 


5 


4 


6 


2 


3 


5 


6 




1863 


4 


4 


2 


4 


7 


7 


2 


7 


6 


9 


7 


7 


4 


4 


4 I 
S 


2 


5 


6 


S 


3 


6 


2 


3 


4 


5 




1864 


5 


5 


7 


S 


7 


7 


6 


7 


7 


9 


2 


7 


4 


4 


2 


4 


2 


4 


10 


S 


6 


6 


8 


4 


6 


S 




1865 


5 


5 


8 


5 


6 


7 


7 


7 


7 


8 


6 


7 


4 


4 


6 


5 


2 


4 


12 


6 


4 


6 


4 


4 


6 


6 




1866 


2 


4 


4 


5 


8 


7 


10 


7 


8 


8 


6 


7 


7 


4 


6 


S 


4 


4 


6 


6 


1 


S 


2 


4 


5 


5 




1867 


8 


S 


2 


5 


12 


7 


4 


7 


14 


9 


4 


6 


9 


5 


4 


5 


3 


4 


2 


6 


2 


S 


2 


4 


6 


6 




1868 


7 


5 





4 





7 


5 


7 


i 


8 


2 


6 





S 


6 


S 


10 


5 


2 


6 


6 


s 


6 


4 


4 


5 




1869 


3 


5 


2 


4 


6 


7 


6 


7 


14 


9 


4 


6 


4 


5 


2 


5 


2 


S 


4 


6 


1 


5 


4 


4 


4 


5 




1870 


5 


5 


10 


S 


6 


7 


2 


6 


5 


9 


3 


6 


5 


5 


7 


5 


4 


4 


6 


5 


4 


5 


8 


4 


5 


5 




1871 


6 


5 


5 


5 


4 


6 


11 


7 


6 


8 


10 


6 


2 


5 


2 


S 


9 


s 


5 


5 


7 


S 


3 


4 


6 


S 




1872 


6 


5 


8 


5 


8 


6 


6 


7 


6 


8 


5 


6 


8 


5 


10 


S 


4 


5 


4 


5 


6 


5 


8 


4 


7 


5 




1873 


4 


5 


4 


5 


11 


7 


8 


7 


8 


8 


6 


6 


2 


5 


4 


S 


4 


5 


4 


5 


7 


5 





4 


5 


5 




1874 


1 


5 


4 


5 


2 


6 


4 


7 


10 


8 


4 


6 


4 


5 


4 


5 


2 


4 


2 


5 


6 


S 


6 


4 


4 


5 




1875 


6 


5 


8 


5 


10 


7 


6 


7 


4 


8 


4 


6 


8 


5 


6 


5 


8 


5 


12 


5 


9 


S 


4 


4 


7 


5 




1876 


4 


5 


8 


S 


5 


7 


8 


7 


9 


8 


4 


6 


2 


5 


6 


S 


6 


5 


8 


6 


9 


6 


12 


4 


7 


5 




1877 


7 


5 


1 


5 


6 


7 


16 


7 


10 


8 


6 


6 


3 


5 


9 


5 


6 


5 


4 


5 


2 


S 


2 


4 


6 


6 




1878 


4 


5 


3 


5 


2 


6 


12 


7 


8 


8 


10 


6 


5 


S 


11 


5 


4 


5 


5 


5 


6 


s 


6 


4 


6 ; 


6 




1879 


10 


5 


10 


5 


10 


6 


14 


8 


6 


8 


10 


6 


6 


5 


7 


5 


2 


5 


4 


S 


6 


5 


2 


4 


7 


6 




1880 


3 


5 


4 


5 


10 


7 


7 


8 


8 


8 


10 


6 


8 


5 


8 


6 


4 


s 


6 


5 


4 


5 


4 


4 


6 


6 




1881 


7 


S 


9 


5 


5 


7 


11 


8 


8 


8 


6 


6 


2 


5 


5 


6 


8 


5 


10 


6 


3 


S 


3 


4 


6 


6 




1882 


2 


S 


3 


5 


3 


6 


12 


8 


8 


8 


5 


6 


2 


5 


3 


5 


4 


5 


10 


6 


5 


5 


8 


4 


5 


6 




1883 


7 


5 


4 


5 


7 


6 


9 


8 


5 


8 


7 


6 


5 


5 


2 


5 


8 


5 


3 


6 


2 


5 


2 


4 


5 


6 




1884 


4 


S 


7 


5 


7 


6 


12 


8 


7 


8 


4 


6 


7 


5 


4 


5 


5 


5 


2 


6 


3 


5 


3 


4 


5 


6 




1885 


8 


5 


4 


5 


5 


6 


9 


8 


7 


8 


5 


6 


5 


5 


10 


s 


3 


5 


7 


6 


8 


S 


3 


4 


6 


6 




1886 


6 


5 


8 


5 


9 


7 


9 


8 


9 


8 


4 


6 


5 


5 


3 


5 


6 


5 


11 


6 


4 


5 


3 


4 


6 


6 




1887 


3 


5 


3 


5 


5 


6 


5 


8 


6 


8 


6 


6 


2 


5 


5 


5 


6 


5 


3 


6 


7 


5 


4 


4 


5 


6 





208 



PROFESSOR C. PIAZZI SMYTH ON 



Table XIII.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Winds — Southern Quarter, J S.E., S., and \ S.W. 





January. 


February. 


March. 


April. 


Mi 


y. 


June. 


July. 


August. 


September 


October. 


November. 


December. 


Mean Month 


Successive 


Year. 


















































of Observed 

Quantities 

in each 

Year. 


Means of 
the Accu- 
mulating 
Years. 


Ob. 


Ac. 

Jin. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Bin, 


(lb. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 

Mn. 


1856 


6 




8 




4 




7 




5 




8 




8 




7 




6 




10 




4 




6 




7 




1857 


6 


6 


12 


IO 


8 


6 


7 


7 


8 


6 


7 


8 


7 


8 


8 


8 


8 


7 


8 


9 


6 


5 


11 


8 


8 


8 


1858 


9 


7 


8 


9 


4 


5 


6 


7 


7 


7 


9 


8 


6 


7 


8 


8 


9 


8 


6 


8 


6 


5 


11 


9 


7 


7 


1859 


9 


8 


8 


9 


6 


6 


4 


6 


8 


7 


6 


8 


7 


7 


10 


8 


10 


8 


6 


8 


8 


6 


8 


9 


8 


8 


1860 


8 


8 


4 


8 


7 


6 


5 


6 


8 


7 


8 


8 


6 


7 


6 


8 


6 


8 


9 


8 


6 


6 


8 


9 


7 


7 


1861 


10 


8 


10 


8 


8 


6 


5 


6 


4 


7 


6 


7 


9 


7 


10 


8 


8 


8 


12 


8 


6 


6 


8 


9 


8 


8 


1862 


10 


8 


8 


8 


6 


6 


9 


6 


10 


7 


7 


7 


8 


7 


8 


8 


8 


8 


9 


9 


9 


6 


9 


9 


8 


8 


1863 


8 


8 


8 


8 


9 


6 


10 


7 


6 


7 


10 


8 


6 


7 


8 


8 


8 


8 


9 


9 


11 


7 


6 


8 


8 


8 


1864 


12 


9 


6 


8 


6 


6 


S 


7 





7 


9 


8 


8 


7 


6 


8 


10 


8 


4 


8 


8 


7 


10 


9 


8 


8 


1865 


6 


8 


6 


8 


6 


6 


8 


7 


10 


7 


6 


8 


9 


7 


9 


8 


9 


8 


5 


8 


7 


7 


10 


9 


8 


8 


1866 


10 


9 


5 


8 


7 


6 


6 


7 


6 


7 


8 


8 


6 


7 


8 


8 


9 


8 


9 


8 


6 


7 


8 


9 


7 


8 


1867 


4 


8 


7 


8 


5 


6 


8 


7 


7 


7 


6 


8 


5 


7 


10 


8 


10 


8 


8 


8 


5 


7 


6 


8 


7 


8 


1868 


8 


8 


7 


7 


9 


7 


7 


7 


12 


7 


9 


8 


8 


7 


9 


8 


5 


8 


8 


8 


7 


7 


10 


8 


8 


8 


1869 


13 


8 


8 


8 


5 


7 


9 


7 


3 


7 


5 


7 


10 


7 


6 


8 


10 


8 


6 


8 


6 


7 


6 


8 


7 


8 


1870 


10 


9 


6 


7 


5 


6 


8 


7 


10 


7 


6 


7 


8 


7 


5 


8 


8 


8 


7 


8 


6 


7 


4 


8 


7 


8 


1871 


11 


9 


8 


7 


8 


6 


5 


7 


6 


7 


5 


7 


12 


8 


10 


8 


6 


8 


10 


8 


4 


7 


8 


8 


8 


8 


1872 


12 


9 


12 


8 


8 


7 


8 


7 


5 


7 


10 


7 


8 


8 


8 


8 


5 


8 


9 


8 


8 


7 


10 


8 


9 


8 


1873 


12 


9 


4 


8 


6 


6 


4 


7 


5 


7 


8 


7 


14 


8 


8 


8 


5 


8 


8 


8 


6 


7 


9 


8 


7 


8 


1874 


8 


9 


11 


8 


8 


7 


10 


7 


5 


7 


7 


7 


10 


8 


8 


8 


11 


8 


9 


8 


7 


7 


4 


8 


8 


8 


1875 


12 


9 


5 


8 


4 


6 


6 


7 


9 


7 


10 


8 


6 


8 


9 


8 


8 


8 


9 


8 


5 


7 


8 


8 


8 


8 


1876 


12 


9 


6 


7 


6 


6 


8 


7 


6 


7 


8 


8 


8 


8 


8 


8 


5 


8 


10 


8 


7 


7 


10 


8 


8 


8 


1877 


5 


9 


4 


7 


6 


6 


6 


7 


6 


7 


10 


8 


9 


8 


6 


8 


4 


8 


9 


8 


10 


7 


8 


8 


7 


8 


1878 


6 


9 


8 


7 


4 


6 


8 


7 


8 


7 


9 


8 


5 


8 


6 


8 


8 


8 


11 


8 


2 


7 


4 


8 


7 


8 


1879 


8 


9 


6 


7 


6 


6 


5 


7 


6 


7 


8 


8 


7 


8 


8 


8 


10 


8 


6 


8 


3 


6 


8 


8 


7 


8 


1880 


10 


9 


10 


7 


8 


6 


7 


7 


4 


7 


5 


8 


5 


8 


7 


8 


8 


8 


2 


8 


6 


6 


5 


8 


6 


8 


1881 


5 


9 


6 


7 


(1 


6 


6 


7 


7 


7 


8 


8 


8 


8 


5 


8 


1 


8 


6 


8 


11 


7 


10 


8 


7 


8 


1882 


10 


9 


7 


7 


6 


6 


6 


7 


8 


7 


8 


8 


12 


8 


7 


8 


8 


8 


8 


8 


6 


7 


7 


8 


8 


8 


1883 


10 


9 


9 


7 


1 


6 


7 


7 


6 


7 


9 


8 


7 


8 


7 


8 


5 


8 


7 


8 


7 


7 


6 


8 


7 


8 


1884 


6 


9 


10 


7 


12 


6 


8 


7 


8 


7 


7 


8 


10 


8 


11 


8 


7 


8 


6 


8 


6 


7 


8 


8 


8 


8 


1885 


9 


9 


9 


8 


•; 


6 


8 


7 


7 


7 


6 


8 


s 


B 


4 


8 


9 


8 


3 


8 


8 


7 


6 


8 


7 


8 


1886 


4 


9 


7 


8 


8 


7 


.'. 


7 


7 


7 


6 


8 


7 


8 


8 


8 


7 


8 


8 


8 


7 


7 


4 


8 


7 


7 


1887 


10 


9 


8 


8 


6 


6 


5 


7 


. r , 


7 


6 


8 


8 


8 


6 


8 


4 


8 


4 


8 


6 


7 


5 


8 


6 


7 



MEAN SCOTTISH METEOROLOGY. 



209 



Table XIV.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Winds — Western Quarter, \ S.W., W., and \ N.W. 



Tear. 


January. 


February 


March. 


April. 


May. 


June. 


July. 


August. 


September October. 


November. December.J Mean Month Successive 
of Observed Means of 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob 


Ac. 

Mil 


Ob. 


Ac. 
Mn 


01, 


Ac 

.Mn 


Ob 


Ac. 

Mn 


01, 


Ac 
Mn 


Ob. 


Ac. 
Mn 


Ob 


Ac. 

Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac 
Mn 


Ob. 


Ac 

Mn 


V^UtlllLlLltS 

in each 
Tear. 


LUC AWU- 

mulating 
Tears. 


1856 


8 




10 




6 




11 




1 




13 




11 




8 




8 




7 




11 




12 




9 




1857 


12 




11 




8 




li 




5 




5 




17 




8 




9 




10 




7 




16 




10 




1858 


15 


IO 


4 


IO 


14 


7 


8 


6 


10 


3 


12 


9 


11 


16 


10 


8 


13 


8 


13 


8 


7 


9 


12 


14 


11 


IO 


1859 


18 


12 
13 


14 


8 
10 


16 


9 
11 


8 


7 
7 


4 


S 
5 


8 


10 

IO 


13 


14 
14 


15 


9 
10 


13 


IO 

II 


8 


IO 

10 


11 


8 
9 


9 


13 

12 


12 


IO 
IO 


1860 


8 




11 




14 




6 




10 




6 




10 




12 




13 




14 




4 




4 




9 




1861 


10 


12 


8 


IO 


16 


12 


8 


7 


12 


6 


6 


9 


12 


J 3 


16 


11 


14 


II 


10 


IO 


11 


8 


11 


11 


11 


IO 


1862 


10 


12 


6 


IO 


4 


12 


10 


7 


in 


7 


12 


8 


15 


13 


10 


12 


9 


12 


15 


IO 


8 


8 


16 


11 


10 


IO 


1863 


14 


12 


14 


9 


10 


i 1 


14 


7 


12 


7 


8 


9 


12 


J 3 


12 


11 


16 


II 


11 


II 


12 


8 


16 


11 


13 


IO 


1864 


8 


12 
II 


8 


IO 

10 


10 


11 
11 


9 


8 
8 


10 


8 

8 


13 


9 
9 


12 


13 
r 3 


12 


11 

11 


13 


12 
12 


6 


II 

IO 


8 


9 
9 


8 


12 
12 


10 


II 
II 


1865 


10 




6 




8 




9 




8 




12 




in 




8 




13 




4 




10 




12 




9 




1866 


15 


II 


10 


9 


8 


11 


5 


S 


10 


8 


8 


IO 


S 


13 


10 


11 


10 


12 


10 


IO 


16 


9 


14 


12 


10 


IO 


1867 


6 


12 


14 


9 


4 


IO 


12 


8 


3 


8 


11 


9 


6 


12 


12 


11 


11 


12 


13 


IO 


13 


10 


14 


12 


10 


IO 


1868 


10 


II 


18 


IO 


16 


IO 


12 


8 


11 


8 


16 


10 


10 


12 


12 


11 


6 


12 


14 


IO 


8 


IO 


8 


12 


12 


IO 


1869 


8 


II 

II 


12 


IO 
IO 


6 


IO 
IO 


9 


9 
9 


3 


8 
8 


11 


IO 

TO 


12 


12 
12 


14 


11 
11 


12 


II 
II 


10 


IO 
IO 


14 


10 

IO 


8 


12 
II 


10 


IO 
IO 


1870 


8 




4 




g 




14 




9 




14 




10 




6 




10 




9 




9 




7 




9 




1871 


8 


II 


11 


IO 


12 


IO 


6 


9 


8 


8 


4 


IO 


12 


n 


12 


11 


5 


II 


10 


IO 


6 


IO 


13 


II 


9 


IO 


1872 


9 


II 


6 


IO 


6 


IO 


8 


9 


10 


8 


10 


10 


7 


12 


6 


11 


12 


II 


10 


IO 


9 


IO 


6 


11 


8 


IO 


1873 


11 


IO 


9 


IO 


6 


IO 


6 


9 


8 


8 


10 


IO 


11 


11 


14 


11 


12 


II 


13 


IO 


10 


IO 


18 


11 


11 


IO 


1874 


18 


IO 
II 


10 


IO 

10 


14 


10 

IO 


12 


9 

9 


6 


8 
8 


12 


IO 

CO 


12 


11 
11 


14 


11 
11 


12 


II 
II 


14 


IO 

II 


10 


IO 
IO 


8 


II 
11 


12 


IO 
IO 


1875 


10 




6 




8 




9 




14 




12 




9 




11 




8 




6 




6 




12 




9 




1876 


10 


II 


8 


IO 


12 


IO 


8 


9 


8 


a 


12 


10 


16 


11 


12 


11 


8 


II 


7 


IO 


6 


IO 


6 


11 


9 


IO 


1877 


10 


II 


15 


IO 


12 


IO 


■2 


9 


8 


s 


11 


TO 


15 


11 


8 


11 


10 


II 


13 


IO 


14 


9 


16 


11 


11 


IO 


1878 


14 


II 


14 


IO 


14 


IO 


6 


3 


8 


8 


6 


TO 


12 


12 


7 


11 


14 


II 


9 


IO 


6 


IO 


8 


11 


10 


IO 


1879 


7 


II 
II 


5 


IO 
IO 


10 


CO 

IO 


4 


8 
8 


9 


8 

8 


7 


IO 
TO 


10 


12 
12 


10 


1 1 
11 


14 


II 

II 


14 


IO 
IO 


9 


9 

9 


12 


11 
11 


9 


IO 
IO 


1880 


12 




11 




8 




9 




10 




7 




9 




8 




12 




8 




12 




13 




10 




1881 


8 


II 


5 


IO 


12 


TO 


5 


8 


10 


8 


10 


IO 


17 


11 


12 


11 


8 


II 


7 


IO 


12 


9 


12 


11 


10 


IO 


1882 


15 


II 


13 


IO 


17 


IO 


7 


8 


8 


8 


9 


IO 


13 


12 


14 


11 


11 


II 


7 


IO 


11 


IO 


8 


II 


11 


IO 


1883 


9 


II 


11 


IO 


7 


TO 


10 


8 


12 


8 


s 


TO 


9 


12 


17 


11 


9 


II 


13 


IO 


14 


10 


14 


11 


11 


IO 


1884 


17 


II 
II 


9 


IO 
IO 


8 


IO 
IO 


3 


S 
8 


12 


9 
9 


12 


TO 
IO 


9 


12 
11 


11 


11 
11 


12 


II 
II 


15 


IO 
IO 


11 


IO 
IO 


14 


11 
11 


11 


IO 
IO 


1885 


8 




11 




11 




8 




8 




12 




13 




/ 




12 




10 




8 




14 




10 




1886 


11 


II 


7 


IO 


8 


IO 


8 


8 


8 


9 


13 


IO 


13 


12 


15 


11 


11 


II 


7 


IO 


12 


IO 


12 


II 


10 


IO 


1887 


13 


II 


11 


IO 


10 


IO 


10 


8 


10 


9 


11 


TO 


15 


12 


11 


11 


10 


II 


13 


IO 

9 


IO 


12 


11 


11 


IO 






II 


| 


IO 


IO 




8 




9 




TO 




12 




11 




II 




IO I 


IO 




11 




IO 



VOL. XXXV. PART 3. 



2 II 



210 



PROFESSOR C. PIAZZI SMYTH ON 



Table XV.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Number of Hours of Sunshine. 





anuary 


February. 


March. 


April, 


May. 


June. 


July. 


August. 


September 


October. 


Nov. 


Dec. 


Mean Month 

of Observed 

Quantities 

in each 


Successive 
Means of 
the Accu- 
mulating 


\ car. 

I 


>b. 


\. . 


Ob. 1 . Ac - 


Ob. 


Ac. 


Ob. 


c. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac 


Ob. 


Ac. 


Hi. 


t C - 


Hi. 


Ac. 






in 




Mil. 




Mil. 




Mil. 




Mn. 




Mn. 




Mn. 




Mn. 




Jill. 




Mn. 




Mn. 




Mn. 


Year. 


Years. 


1856 






















































1857 


75 




S9 




92 




136 




177 




277 




207 




209 




148 




115 




73 




67 




139 




1858 


hm 


:-' 


115 


I02 


138 


"5 


198 


167 


185 


181 


260 


268 


217 


212 


218 


214 


1S3 


166 


114 


114 


71 


74 


54 


60 


152 


146 


1859 


Nil 


7° 


75 


93 


119 


116 


166 


167 


301 


221 


239 


259 


222 


215 


210 


212 


164 


165 


108 


112 


86 


78 


61 


61 


151 


147 


1860 


64 


c,s 


105 


96 


132 


120 


194 


174 


205 


217 


175 


238 


202 


212 


154 


198 


153 


162 


107 


in 


68 


75 


61 


61 


135 


144 


1861 


58 


66 


87 


94 


147 


126 


179 


175 


197 


J 13 


223 


235 


208 


211 


157 


190 


130 


156 


127 


114 


81 


76 


80 


65 


140 


143 


1862 


50 


64 


80 


92 


SO 


118 


183 


176 


182 


208 


174 


225 


200 


209 


156 


184 


157 


156 


139 


n8 


108 


82 


59 


64 


131 


141 


1863 


ii'.i 


64 


111 


95 


138 


121 


163 


174 


196 


206 


198 


221 


261 


217 


183 


184 


134 


*53 


112 


117 


84 


82 


62 


63 


143 


141 


1864 


78 


66 


108 


96 


125 


121 


191 


176 


2:17 


2IO 


214 


220 


221 


217 


213 


188 


163 


i54 


99 


"5 


77, 


81 


55 


62 


148 


142 


1S65 


70 


'•7 


70 


93 


128 


122 


194 


178 


176 


206 


250 


223 


226 


2l8 


141 


182 


195 


J 59 


111 


"5 


90 


82 


64 


63 


143 


142 


1866 


70 


"7 


101 


94 


129 


123 


161 


176 


260 


212 


229 


224 


207 


217 


146 


179 


133 


156 


99 


"3 


97 


84 


56 


62 


141 


142 


1867 


78 


68 


94 


94 


136 


123 


118 


171 


143 


205 


196 


221 


168 


213 


174 


178 


134 


r 54 


115 


"3 


94 


85 


US 


62 


126 


141 


1868 


53 


"7 


89 


94 


130 


124 


141 


109 


211 


206 


264 


225 


275 


2l8 


183 


179 


124 


1 5 2 


123 


114 


67 


83 


7N 


62 


143 


141 


1869 


49 


65 


S4 


93 


157 


127 


202 


171 


176 


204 


214 


224 


217 


2l8 


206 


181 


118 


149 


102 


"3 


79 


83 


72 


63 


140 


141 


1870 


68 


66 


72 


91 


132 


127 


185 


172 


180 


202 


205 


223 


240 


219 


240 


185 


182 


151 


122 


114 


92 


83 


59 


63 


14S 


141 


1871 


67 


66 


64 


90 


131 


128 


121 


169 


250 


20S 


217 


222 


208 


219 


227 


188 


153 


I 5 I 


104 


113 


78 


83 


75 


63 


141 


141 


1872 


HI 


65 


78 


89 


108 


126 


151 


168 


169 


203 


175 


219 


229 


219 


161 


186 


110 


149 


127 


114 


75 


83 


56 


63 


125 


140 


1873 


66 


65 


101 


90 


113 


126 


165 


168 


208 


203 


207 


219 


216 


219 


177 


186 


167 


I 5° 


122 


114 


7.1 


82 


75 


64 


141 


140 


1874 


74 


66 


103 


90 


138 


126 


179 


168 


170 


20I 


277 


222 


239 


220 


188 


186 


145 


150 


140 


116 


78 


82 


84 


65 


151 


141 


1875 


18 


65 


75 


90 


119 


126 


198 


170 


203 


201 


192 


220 


250 


222 


174 


185 


143 


149 


90 


"5 


71 


81 


HI 


65 


136 


141 


1876 


■ II 




92 




102 




132 




246 




265 




230 




232 




118 




74 




62 




26 




137 








65 




90 




125 




168 




204 




223 




222 




187 




148 




112 




80 




63 




141 


1877 


60 




98 




126 




135 




192 




231 




168 




129 




166 




115 




87 




55 




130 








65 




90 




125 




166 




203 




223 




220 




185 




149 




"3 




81 




62 




140 


1878 


7! 




77 




107 




168 




198 




242 




237 




174 




153 




108 




84 




71 




144 








65 




89 




125 




166 




203 




224 




220 




184 




149 




112 




81 




63 




140 


1879 


71 


65 


62 


88 


101 


124 


121 


164 


178 


202 


155 


221 


144 


217 


165 


183 


141 


148 


131 


"3 


95 


81 


71 


63 


120 


139 


1880 


58 


65 


92 


88 


155 


126 


147 


163 


223 


203 


230 


221 


194 


2l6 


198 


184 


16G 


149 


130 


114 


85 


82 


51 


63 


144 


140 


1881 


'-1 




64 




123 




171 




235 




186 




167 




158 




103 




91 




53 




7,1 




124 








66 




87 




126 




164 




204 




220 




214 




183 




147 




"3 




80 




62 




1.39 


1882 


7.7 


65 


72 


87 


113 


125 


138 


163 


248 


206 


188 


219 


198 


214 


190 


183 


137 


147 


95 


112 


m 


80 


45 


61 


128 


139 


1883 


HI 


6S 


81 


87 


140 


126 


164 


163 


210 


206 


213 


218 


197 


213 


178 


183 


131 


146 


119 


"3 


7! 


80 


52 


61 


135 


138 


1884 


17 


'M 


70 


86 


95 


125 


136 


162 


180 


20S 


178 


2T7 


157 


211 


196 


183 


138 


146 


95 


1 12 


mi 


79 


to 


60 


116 


138 


1885 


36 


64 


83 


86 


118 


I24 


155 


162 


144 


203 


207 


217 


228 


211 


165 


183 


133 


146 


99 


in 


18 


78 


55 


60 


123 


137 


1886 


52 




66 




98 




175 




145 




218 




198 




150 




132 




74 




7S 




63 




120 








63 




85 




123 




162 




20 1 




217 




211 




182 




r 45 




no 




78 




60 




136 


1887 


:,u 


63 


89 


85 


131 


124 


160 


162 


201 


20I 


236 


217 


207 


211 


186 


[82 


128 


145 


112 


no 


15 


77 


in 


60 


133 


136 



MEAN SCOTTISH METEOROLOGY. 



211 



Table XVI.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

' Mean Amount op Cloud. 





January. 


February. 


March. 


April. 


May. 


June. 


July. 


August. 


September 


October. 


November. 


December. 


Mean Month 

of Observed 

Quantities 

in each 


Successive 
Means of 
the Accu- 
mulating 


Year. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 


Ob. 


Ac. 






Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 


Year. 


Years. 


1856 






















































1857 


6-3 




6-4 




7-2 




6-7 




6-3 




5-0 




6-3 




5-9 




6-3 




6-4 




6-9 




6-3 




6-3 




1858 


6 3 


6'3 


5-1 


5-8 


5-6 


6-4 


5-4 


6-o 


6-3 


6-3 


5-4 


S' 2 


6-1 


6-2 


5-8 


5-8 


5-6 


6-o 


6-7 


6-6 


6-7 


6-8 


6-9 


6-6 


6-0 


6-2 


1859 


6-4 


6-3 


6-6 


6-o 


6-3 


6-4 


6-2 


6-1 


4-0 


S'S 


5-8 


5'4 


6-2 


6-2 


5-8 


5-8 


6-0 


6-o 


6-6 


6-6 


6-5 


67 


6-7 


6-6 


6-1 


6-i 


1860 


6-9 


6-5 


6-0 


6-0 


6-3 


6-4 


5-5 


6-o 


6-2 


5 '7 


6-9 


S'S 


6-5 


6'3 


67 


6-o 


6-1 


6-o 


6-6 


6-6 


6-9 


6-8 


6-8 


67 


6-4 


6-2 


1861 


7 3 


6-6 


6-2 


6-i 


6 


6-3 


6-0 


6-o 


6-4 


5'8 


6 3 


S"9 


6 '6 


6-3 


7-0 


6-2 


6-9 


6-2 


6-0 


6-5 


6 3 


67 


5-9 


6-5 


6-4 


6-2 


1862 


7-5 


6-8 


6-9 


6-2 


7-6 


6-5 


6-2 


6-o 


6-6 


6'o 


6-9 


6-o 


7-0 


6 ' 4 


7-2 


6-4 


6-2 


6-2 


5-9 


6-4 


5-7 


6-5 


6-9 


6-6 


6-7 


6-3 


1863 


6-8 


6-8 


5-8 


6-i 


6-5 


6-5 


6-5 


6-i 


6-8 


6-i 


6-8 


6-2 


5-8 


6-4 


7-0 


6-5 


67 


6-2 


6-8 


6-4 


6-5 


6-5 


6 6 


6-6 


6-6 


6-4 


1864 


6-2 


67 


5-7 


6-i 


6-6 


6"5 


5-9 


6-i 


6-0 


6-i 


6-7 


6-2 


6-6 


6-4 


6-1 


6-4 


6-0 


6-2 


7-0 


6'5 


6-8 


6'5 


7-2 


67 


6-4 


6-4 


1865 


6-2 


67 


7-1 


6-2 


6-4 


6-5 


5-9 


6-o 


6-7 


6-i 


5-6 


6-2 


6-0 


6-3 


7-2 


6'5 


5-2 


6'i 


6-3 


6'5 


6-3 


6-5 


6-5 


6-6 


6-3 


6-4 


1866 


6-5 


6-6 


5-9 


6-2 


6-6 


6'5 


6-3 


6-i 


5-1 


6'i 


6-2 


6-2 


6-6 


6- 4 


7-2 


6-6 


6-6 


6'2 


6-8 


6\5 


6-0 


6-5 


7-1 


67 


64 


6-4 


1867 


6-5 


6-6 


6 ; 5 


6-2 


6-1 


6-5 


7-6 


6-2 


7-6 


6-2 


6-8 


6-2 


7-3 


6'5 


6-8 


6-6 


6-6 


6-2 


6-5 


6'5 


6-1 


6- 4 


6 7 


67 


6-8 


6-4 


1868 


7-1 


67 


6-7 


62 


6-6 


6-5 


7-2 


6-3 


6-4 


6-2 


5-8 


6-2 


5-5 


6-4 


6-6 


6-6 


6 '9 


6'3 


5-9 


6'5 


6-8 


6'5 


6-8 


67 


6-5 


6-4 


1869 


7 - 5 


67 


6-7 


6-3 


57 


6-4 


5-8 


6-2 


6-6 


6-2 


6-6 


6-2 


6-5 


6-4 


5-9 


6'6 


6-9 


6'3 


6-7 


6-5 


6-2 


6-4 


6-1 


6-6 


6-4 


6-4 


1870 


67 


67 


7'3 


6-4 


6-4 


6-4 


5-8 


6-2 


6-7 


6'3 


6-4 


6-2 


6-3 


6-4 


5-3 


6-5 


5-6 


6'3 


5-9 


6-4 


6-0 


6-4 


6-9 


67 


6-3 


6-4 


1871 


6-6 


67 


77 


6-4 


6-0 


6-4 


7-2 


6-3 


5-4 


6-2 


6-5 


6-2 


6-6 


6-4 


57 


6-4 


6-4 


6-3 


6-6 


6-4 


6-4 


6-4 


6-3 


6-6 


6-4 


6-4 


1872 


7-1 


67 


7-2 


6-5 


7-0 


6-4 


6-7 


6-3 


6-9 


6-2 


7-2 


6-3 


6-5 


6-4 


6-8 


6-4 


71 


6-3 


6-2 


6-4 


6-7 


6-4 


7-2 


67 


6-9 


6-4 


1873 


67 


67 


5-8 


6-4 


6 9 


6'5 


6-4 


6'3 


6-5 


6-3 


6-7 


6-3 


6-5 


6-3 


7-0 


6'5 


6-1 


6-3 


6-4 


6- 4 


6-7 


6-4 


6-6 


67 


6-6 


6-4 


1874 


6-3 


67 


5-9 


6-4 


6 2 


6-4 


5-9 


6-3 


6-6 


6-3 


4-9 


6-2 


6-1 


6-4 


6-2 


S'S 


6 '6 


6-3 


5-8 


6-4 


6-6 


6-4 


5-4 


6-6 


6-0 


64 


1875 


7 "5 


6'8 


6-6 


6-4 


67 


6"5 


5 3 


6-2 


6-0 


6-3 


6 3 


6-3 


5-4 


6-3 


6-9 


6-5 


6 3 


6'3 


6-9 


6-4 


6-2 


6-4 


6-6 


6-6 


6-4 ' 


6-4 


1876 


6-6 


6-8 


61 


6-4 


6-8 


6-5 


6-7 


6-3 


5-3 


6-2 


5-1 


6-2 


6-0 


6-3 


5-2 


6-4 


6 9 


6-4 


7-2 


6-5 


6-6 


6-4 


8-0 


67 


6-4 


6-4 


1877 


7-0 


6-8 


5-9 


6-4 


6-3 


6-5 


67 


6-3 


6-5 


6-2 


5-9 


6-2 


7-1 


6-4 


7-2 


6-4 


5-9 


6'3 


6-6 


6-5 


6-1 


6- 4 


6-6 


67 


6 '5 


6-4 


1878 


6-2 


67 


6-7 


6-4 


5-6 


6- 4 


6-2 


6'3 


6-5 


6'3 


5-5 


6-2 


6-3 


6-4 


6-5 


6-4 


6-1 


6-3 


6-5 


6'5 


6-0 


6-4 


4-9 


6-6 


6-1 


6 ' 4 


1879 


5-9 


67 


6-9 


6-4 


6-5 


6-4 


6-8 


6-3 


6-0 


6-2 


7-3 


6-2 


7-8 


6- 4 


6-7 


6-5 


6-0 


6-3 


5-9 


6-4 


6-0 


6-4 


5-8 


6-6 


6 '5 


6-4 


1880 


6-7 


6 7 


6-6 


6-4 


5-6 


6-4 


6-4 


6-3 


5-9 


6-2 


5-9 


6'2 


7-0 


6-4 


6-2 


6-5 


5-9 


6'3 


5-6 


6-4 


5-9 


6-4 


6-7 


6-6 


6-2 


6-4 


1881 


57 


67 


7-4 


6-5 


6-5 


6-4 


6-2 


6 '3 


5 2 


6-2 


6-5 


6-2 


7-3 


6"5 


6-7 


6-5 


7-3 


6-3 


6-4 


64 


7-0 


6-4 


6-2 


6-5 


6-5 


6-4 


1882 


6-9 


6 7 


6-9 


6-5 


6-6 


6-4 


6-5 


6'3 


5-2 


6-i 


6-6 


6-2 


6-7 


S'S 


6-6 


6-5 


6-5 


6-3 


6-9 


6-4 


6-5 


6-4 


7-1 


6-6 


6-6 


64 


1883 


6-9 


67 


6-9 


6'5 


5-9 


6-4 


6-5 


6'3 


6-6 


6-2 


6-7 


6-2 


6 '9 


6-5 


6-6 


6-5 


6-8 


6-4 


6-0 


6-4 


6-6 


6-4 


6-6 


6-6 


6-6 


6-4 


1884 


7-5 


67 


6-8 


6-5 


6-8 


6-4 


6 '3 


6-3 


6-0 


6-2 


6-4 


6-2 


7-0 


6-5 


6-0 


6-5 


6-0 


6'3 


6-5 


6-4 


6-3 


6-4 


6-7 


6'6 


6 5 


6-4 


1885 


6-9 


67 


6-1 


6-5 


6-1 


6-4 


5-9 


6'3 


6-6 


6-2 


61 


6-2 


5-8 


6'5 


63 


6'5 


6-2 


6-3 


6-2 


6- 4 


6-6 


6- 4 


6-0 


6-6 


6-2 


6-4 


1886 


6-6 


67 


6-7 


6-5 


6-6 


6-4 


5-8 


6'3 


6-9 


6'2 


5-8 


6-2 


6-5 


6-5 


6-7 


6-5 


6-1 


6-3 


7-0 


6-4 


6-2 


6-4 


5-7 


6-5 


6-4 


6-4 


1887 


6-7 




61 




6-0 




5-6 




6-3 




5-6 




6-8 




6-5 




6-4 




5-9 




7-2 




6-5 




6-3 








67 




6-5 


6-4 




6-3 




6-2 




6-2 




6-5 




6-S 




6-3 




6-4 




6-4 




6-5 




6-4 



212 



PROFESSOR C. PTAZZI SMYTH ON 



Tabus XVI I.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Lightning. — Mean Number of Days on which Lightning was seen or Thunder heard at 

Reporting Stations. 



the 



■* ear. 


January, 


February 


March. 


April. 


May. 


June. 


July. 


August. 


Sept. 


October. 


November. 


December. 


Mean Month 

of Observed 

Quantities 

in each 

Year. 


Successive 
Means of 

the Accu- 
mulating 
Years. 




Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


A 0. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac 

Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 
Mn. 


Ob. 


Ac. 

Mn. 


Ob. 


Ac. 
Mn. 


1856 






















































1857 






















































185S 






















































1859 






















































1860 


1 




1 




1 








2 




3 




2 




1 




1 




2 




2 




1 




1'5 




1861 


1 









1 








1 




2 




3 




1 




1 




1 




2 




1 




1'2 




1862 


2 


i"o 


1 


o-5 


1 


I'O 




I'O 


2 


i'S 


2 


2 "5 


2 


2 - S 


1 


I'O 


1 


I'O 


4 


1 '5 


1 


2'0 


2 


I'O 


1-8 


1 '4 


1863 


2 


i'3 


1 


07 


1 


I'O 




1 '3 


1 


17 


2 


2 "3 


1 


2 '3 


2 


I'O 


1 


I'O 


1 


2 '3 


1 


17 


2 


1 '3 


1-3 


i'S 


1864 


2 


i "5 
i-6 


2 


o-8 
i"o 


1 


I'O 
I'O 




I '2 

i'6 


2 


i'S 

i'6 


2 


2 '2 
2 '2 


1 


2'0 

i'8 


1 


I '2 
I '2 


2 


I'O 
I "2 


1 


2'0 

i'8 


1 


I'S 
1 '4 


2 


1 '5 
i-6 


1-7 


1 '4 
i'S 


1865 


2 




1 




1 








2 




1 




2 




2 




1 




1 




2 




2 




1-5 




1866 


2 


i'7 


2 


I'O 


1 


I'O 




I'S 


1 


17 


2 


2'0 


2 


i'8 


2 


1 '3 


2 


I "2 


1 


17 


1 


1 '5 


2 


i'7 


1-6 


i'S 


1867 


1 


i'7 


2 


I'l 


1 


I'O 




1 '4 


2 


c-6 


2 


2'0 


2 


1 '9 


2 


1 '4 


2 


1 '3 


2 


i-6 


1 


1 '4 


2 


i'7 


17 


1 '5 


1868 


2 


r6 


2 


I "2 


1 


I'O 




1 '4 


3 


i-6 


2 


2'0 


2 


1 '9 


2 


1 '5 


1 


1 '4 


2 


i'6 


1 


1 '4 


1 


i-8 


1-8 


i'S 


1869 


1 


17 
i-6 


1 


1 "3 
1 '3 


1 


I'O 
I'O 




1 '4 
1 '4 


1 


i-8 
17 


2 


2'0 
2'0 


2 


1 '9 

1 "9 


2. 


i-6 
i'6 


2 


1 '3 

i"4 


1 


17 
i-6 


2 


1 '3 
1 '4 


1 


i'7 
i'6 


1-4 


i'6 
1 '5 


1870 


2 









1 








2 




2 




2 




2 




1 




2 




2 




1 




1-5 




1871 


2 


i-6 


1 


I '2 


2 


I'O 




1 '4 


1 


17 


3 


2'0 


4 


1 '9 


1 


i-6 


1 


1 '4 


2 


1 '6 


1 


1 '5 


1 


i'S 


1'7 


1 '5 


1872 


2 


17 


1 


I - 2 


1 


I'l 




1 '3 


3 


17 


2 


2'l 


3 


2'I 


3 


i'6 


3 


1 '3 


2 


17 


2 


1 '4 


1 


i'S 


2-0 


1 '6 


1873 


2 


17 


1 


I '2 


4 


I'l 




1 "3 


1 


i-8 


2 


2'I 


4 


2 '2 


3 


i'7 


2 


i'S 


2 


i7 


3 


i'S 


2 


1 '5 


2-2 


i'6 


1874 


2 


17 
17 


1 


I"I 
I'l 


2 


1 '3 
1 '3 




1 '3 
1 '3 


2 


17 
17 


3 


2'I 

2'I 


3 


2 '3 
2' 3 


3 


r8 
1 '9 


2 


i'S 
i'S 


■2 


17 

17 


1 


i-6 
i'S 


1 


i'S 

i'S 


2-0 


i'6 
i'7 


1875 


2 









2 








2 




2 




2 




2 




1 




1 




1 




2 




1-5 




1876 


1 


r8 


2 


I"I 


2 


1 "4 




1 "3 


2 


i'8 


2 


2'I 


1 


2'3 


1 


1 '9 


1 


i'S 


1 


17 


1 


i'6 


1 


1 '5 


1-3 


r6 


1877 


2 


17 


2 


I'l 




i'4 




1 "3 


1 


i'8 


3 


2'I 


2 


2 '2 


2 


i'8 


1 


i'S 


2 


i'6 


2 


i'S 


1 


i'S 


1-8 


r6 


1878 


1 


17 




I '2 




1 '4 




1 '3 


3 


17 


2 


2 '2 


2 


2'2 


3 


i'8 


1 


1 "4 


'2 


17 


1 


i'S 


2 


1 '4 


1-7 


i'6 


1879 


1 


17 
i-6 




I '2 
I '2 




1 '4 

1 '4 




i'3 

1 "3 


1 


i'8 

i'8 


4 


2'2 
2'2 


1 


2 "2 
2 '2 


3 


1 '9 

2'0 


1 


1 '4 
1 '4 


1 


i'7 

i'7 


1 


1 '5 

1 '4 


1 


i'S 
1 '4 


1-4 


i'6 

r6 


1880 


1 
















1 




4 




4 




1 









1 




2 




1 




1-5 




1881 





i-6 




I'l 




1 '3 




1 '3 


2 


17 


2 


2 '3 


2 


2 '2 


1 


2'0 


1 


1 '3 


1 


i'6 


3 


i'S 


1 


1 '4 


1-3 


i'6 


1882 


l 


i'5 




I'l 




1 '3 




1 '3 


2 


17 


3 


2'3 


5 


2 '2 


2 


I '9 


1 


1 '3 


1 


i'6 


2 


i'S 


2 


1 '4 


1-8 


i-6 


1883 


2 


!'■- 




I'l 




1 '3 




1 '3 


1 


17 


2 


2 "3 


4 


2 - 3 


1 


1 '9 


2 


1 '3 


'2 


i'6 


2 


i'6 


1 


1 '4 


1'7 


i'6 


1884 


2 


1 "5 
i-6 




I'l 
I'l 




1 '3 
i - 3 




I '2 

1 "3 


2 


17 
17 


2 


2 '3 

2 '3 


6 


2 '4 

2 7 


3 


i'8 
1 -9 


2 


1 '3 
1 '4 


1 


i'6 

i-6 


1 


i'6 
r6 


2 


1 '4 
1 '4 


2-1 


i'6 
i'6 


1885 


1 
















3 




2 




2 




1 




2 




1 




1 




1 




1-4 




1886 


2 


i'S 




I'l 





1 "3 




i'3 


1 


,■:: 


2 


2 '3 


2 


2 '5 


1 


i'8 


1 


1 '4 


2 


1 '5 


1 


i'S 


2 


1 '4 


1-2 


i'6 


1887 


l 


r6 
i'S 




I'l 
I'l 




I '2 
I '2 




I '2 
I '2 


1 


17 
17 


1 


2 "3 
2 '2 


2 


2'S 

2-S 


2 


i'8 

i'8 


2 


1 '4 
1 '4 


1 


i-6 

i'S 


1 


i'S 


2 


1 '4 
i'S 


1-3 


[■6 
i'6 



MEAN SCOTTISH METEOROLOGY. 



213 



Table XVIII. —SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Lightning. — Number of Stations at which Lightning was seen or Thunder heard. 





Jan. 


Feb. 


March. 


April 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Not. 


Dec. 


j 

Mean Month'Successive 


Ace. 


Year. 


























of Observed 

Quantities 

in each 

Year. 


Means ol 
the Accu- 
mulating 
Years. 


Days 


Mns. 

Da. 

X 

Sta. 


Ob. 


Ac. 
Mn. 


Ob 


Ac. 
Mn 


Ob 


Ac 

Mn 


Ob. 


Ac 
Mn 


Ob 


Ac 
Mn 


Ob. 


Ac 
Mn 


Ob. 


Ac. 
Mn 


Ob 


Ac. 

Mn 


Ob 


Ac 

Mn. 


Ob 


(Ac 
Mn 


Ob 


Ac. 
Mn 


Ob 


Ac. 
Mn 


X 

Stations 


1856 




















































1 




1857 


























































1858 


























































1859 


























































1860 


13 




10 




9 




4 




26 




37 




20 




16 




7 




12 




2 




6 




14 




21-0 




1861 


3 


8 





5 


32 


20 


10 


7 


16 


21 


28 


32 


40 


3° 


17 


16 


8 


8 


20 


16 


20 


II 


11 


8 


17 


: 15 


20-4 


20*7 


1862 


18 


II 


1 


4 


1 


14 


10 


8 


34 


2 5 


20 


28 


31 


3° 


21 


18 


16 


IO 


23 


18 


12 


II 


18 


12 


17 


16 


30-6 


24 - o 


186 3 


20 


14 


34 


11 


6 


12 


16 


10 


13 


22 


25 


28 


15 


26 


28 


20 


24 


H 


31 


22 


7 


IO 


20 


14 


20 


17 


26-0 


24"5 


1864 


6 


12 


8 


11 


4 


IO 


2 


8 


36 


25 


33 


29 


19 


2 5 


16 


20 


9 


13 


1 


17 


21 


12 


8 


J 3 


14 


16 


23-8 


24-4 


1865 


14 


12 


3 


9 


5 


IO 


9 


8 


33 


26 


11 


26 


35 


27 


24 


20 


3 


11 


6 


16 


4 


11 


14 


!3 


13 


16 


19-5 


236 


1866 


23 


14 


•29 


12 


1 


8 


11 


9 


9 


24 


27 


26 


41 


29 


24 


21 


25 


x 3 


5 


14 


4 


IO 


12 


*3 


18 


16 


28-8 


24 '3 


1867 


17 


H 


•21 


J 3 


5 


8 


5 


8 


23 


2 4 


28 


26 


37 


3° 


36 


23 


26 


15 


6 


J 3 


3 


9 


7 


12 


18 


16 


30-6 


25 - i 


1868 


26 


16 


19 


14 


5 


8 


27 


IO 


42 


26 


29 


26 


9 


27 


36 


24 


31 


17 


17 


*3 


13 


IO 


6 


11 


22 


17 


39-6 


267 


1869 


18 


16 


7 


J 3 


7 


8 


26 


12 


3 


24 


8 


25 


28 


28 


12 


23 


19 


17 


18 


14 


10 


10 


5 


11 


13 


17 


18-2 


25-8 


1870 


4 


15 





12 


1 


7 


6 


11 


6 


22 


17 


24 


33 


28 


34 


24 


12 


16 


6 


x 3 


14 


IO 


2 


10 


11 


16 


16-5 


25-0 


1871 


9 


14 


12 


12 


14 


8 


15 


12 


6 


21 


39 


25 


40 


29 


19 


24 


5 


15 


10 


l 3 


3 


9 


6 


IO 


15 


16 


25-5 


25-0 


1872 


15 


14 


22 


13 


4 


7 


32 


13 


24 


21 


36 


26 


36 


3° 


31 


24 


40 


x 7 


21 


14 


10 


9 


5 


9 


23 


17 


46 


267 


1873 


16 


14 


1 


12 


1 


7 


9 


13 


11 


20 


25 


26 


39 


3° 


32 


25 


28 


18 


29 


15 


3 


9 


13 


IO 


17 


17 


37-4 


27-4 


1874 


12 


14 


2 


11 


12 


7 


24 


14 


11 


20 


40 


27 


33 


3° 


34 


2 5 


27 


19 


3 


14 


8 


9 


8 


9 


18 


17 


36-0 


28-0 


1875 


11 


14 





11 


2 


7 


8 


J 3 


15 


20 


25 


27 


21 


3° 


28 


25 


21 


!9 


17 


J 4 


3 


8 


IS 


10 


14 


16 


21-0 


27 '6 


1876 


8 


H 


7 


10 


4 


7 


12 


x 3 


12 


*9 


24 


27 


29 


3° 


14 


25 


16 


J 9 


25 


15 


3 


8 


7 


IO 


13 


16 


16-9 


26 - 9 


1877 


15 


14 


5 


10 


5 


7 


27 


14 


7 


18 


32 


27 


28 


3° 


26 


2 S 


13 


18 


17 


15 


12 


8 


6 


IO 


16 


16 


28-8 


27-0 


1878 


14 


14 


2 


10 


4 


6 


3 


13 


34 


!9 


37 


27 


17 


29 


33 


25 


5 


18 


4 


I 4 


4 


8 


11 


IO 


14 


16 


23-8 


26 "9 


1879 


2 


13 


2 


9 


1 


6 


13 


13 


16 


19 


35 


28 


26 


29 


35 


26 


9 


17 


4 


14 


9 


8 


4 


9 


13 


16 


18-2 


26 - 4 


1880 


7 


13 


2 


9 


6 


6 


13 


J 3 


4 


18 


31 


28 


36 


29 


18 


2 S 





16 


7 


13 


10 


8 


7 


9 


12 


16 


18-0 


26 'O 


1881 





12 





9 


2 


6 


11 


J 3 


36 


J 9 


23 


28 


23 


29 


11 


25 


4 


16 


6 


I 3 


26 


9 


3 


9 


12 


16 


15-6 


25 \5 


1882 


8 


12 


6 


8 


9 


6 


4 


13 


30 


20 


35 


28 


36 


29 


2S 


2 S 


17 


16 


15 


13 


18 


IO 


9 


9 


18 


16 


32-4 


25'9 


1883 


4 


12 


7 


8 


9 


6 


3 


12 


6 


J 9 


24 


28 


32 


29 


14 


24 


23 


16 


23 


14 


24 


IO 


8 


9 


15 


16 


25-5 


25-8 


1884 


20 


12 


10 


8 


5 


6 


29 


13 


25 


19 


15 


27 


34 


29 


39 


25 


28 


17 


7 


13 


16 


IO 


18 


9 


20 j 


16 


42-0 


26-5 


1885 


4 




2 




1 




8 




27 




12 




14 




19 




28 




5 




3 




5 




11 


16 


15-4 


26 - I 


1886 


17 


12 


5 


8 





6 





13 


8 


20 


16 


27 


25 


29 


20 


2 5 


19 


17 


19 


13 


4 


10 


9 


9 


12 


14-4 


18871 4 


12 


13 


8 


2 


6 


18 


12 


3 


19 


21 


26 


29 


29 


29 


25 


20 


17 


2 


13 


6 


IO 


4 


9 


13 


16 


16-9 


25-6 


) 


12 




8 




i 




13 




19 




26 




29 




25 




17 




13 




IO 




9 




is 




25'3 


vo 


L. 3 


:xx 


V. 


PA 


RT 


3. 








































5 


! I 





214 



PROFESSOR C. PIAZZI SMYTH ON 



Table XIX.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Aurora. — Mean Number op Days on which Aurora was observed at the Reporting Stations. 





Jan. 


Feb. 


March. 


April. 


May. 


June. 


Jnly. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Mean Month 

of Observed 

Quantities 


Successive 
Means of 
the Accu- 


Year. 


























I 


















Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob, 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


Ob. 


Ace. 


in each 


mulating 






Mn. 




Sin. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 




Mn. 


Year. 


Years. 


1856 






















































1857 






















































1858 






















































1859 






















































1860 


2 




3 




3 




2 









1 









3 




2 




2 




2 




1 




1-8 




1861 


2 


2'o 


2 


2*5 


2 


2'5 


2 


2"o 


6 


3"° 





°"5 


1 


°'S 


] 


2'0 


5 


3 '5 


3 


2 '5 


2 


2'0 


3 


2'0 


2-4 


2'I 


1862 


2 


2'o 


2 


2 "3 


2 


2- 3 


2 


2'o 


1 


2- 3 





o'3 





°'3 


3 


2 '3 


2 


3'° 


3 


27 


4 


2'7 


2 


2'0 


1-9 


2'0 


1863 


2 


2 - 


2 


2'2 


2 


2'2 


3 


2 "2 


1 


2'0 





0'2 





0'2 


2 


2 '2 


2 


2-8 


2 


2'S 


3 


2'8 


3 


2 '2 


1-8 


2'0 


1864 


2 


2X> 


2 


2 '2 


3 


2 '4 


2 


2'2 


1 


I "8 


1 


°'4 


1 


o'4 


o 


2 '2 


3 


2'8 


■2 


2 -4 


2 


2'6 


2 


2'2 


1-9 


2'0 


1865 


4 


2 '3 


2 


2 '2 


2 


2 '3 


2 


2'2 


2 


i-8 





o'3 


1 


°'5 


2 


2 '2 


4 


3"° 


3 


2'S 


3 


2'7 


3 


2 '3 


2-3 


2'0 


1866 


7 


3'° 


4 


2 - 4 


2 


2 "3 


3 


2'3 


1 


i'7 





o'3 


1 


o'6 


1 


2'0 


3 


3'° 


2 


2 -4 


3 


27 


2 


2- 3 


2-4 


2'I 


1867 


2 


2*9 


2 


2 '4 


3 


2'4 


3 


2 '4 


2 


1-8 





0'2 





°'5 


2 


2'0 


3 


3'° 


3 


2 '5 


3 


2'8 


2 


2 '2 


21 


2'I 


1868 


2 


2-8 


3 


2 '4 


2 


2-3 


2 


2 - 3 


2 


i-8 





0'2 





°'4 


2 


2'0 


3 


3'° 


3 


2'6 


2 


27 


2 


2 '2 


1-9 


2'I 


1869 


2 


2 '7 


3 


2\5 


3 


2 "4 


2 


2 '3 


1 


1 7 





0'2 





°'4 


2 


2'0 


3 


3'o 


2 


2'S 


3 


27 


3 


2 '3 


2-0 


2'0 


1870 


3 


27 


2 


2\5 


4 


2\5 


4 


2\5 


1 


i-6 





0'2 


1 


°'5 


3 


2'I 


3 


3"° 


4 


2'6 


3 


27 


3 


2 ' 4 


2-6 


2'I 


1871 


4 


2-8 


3 


2\5 


2 


2 '5 


2 


2 '4 


1 


i-6 





0'2 





o'4 


2 


2'I 


2 


2 -9 


2 


2'6 


2 


27 


3 


2 -4 


1-9 


2'I 


1872 


2 


2-8 


1 


2 "4 


4 


2-6 


2 


2 "4 


1 


i "5 





0'2 


1 


°'S 


2 


2'I 


2 


2'8 


3 


2'6 


4 


2'8 


3 


2 '5 


2'1 


2'I 


1873 


3 


2-8 


3 


2 "4 


1 


2-5 


2 


2-4 





i\5 





O'l 





o'4 


1 


2'0 


3 


2 '9 


3 


2'6 


2 


27 


1 


2 -4 


1-6 


2'I 


1874 


2 


2 7 


2 


2 "4 


2 


2'5 


2 


2- 3 


1 


i '4 





O'l 





o' 4 


2 


2'0 


2 


2'8 


2 


2'6 


2 


27 


2 


2 '3 


1-6 


2'0 


1875 


1 


2-6 


2 


2-4 


2 


2 - 4 


1 


2'2 


1 


i '4 





O'l 





o'4 


1 


2'0 


2 


2'8 


2 


2'6 


2 


2'6 


1 


2 '2 


1-2 


2'0 


1876 


2 


2-6 


1 


2 3 


1 


2-4 





2"I 





i '3 





O'l 





o'4 


4 


2"I 


3 


2'8 


1 


2'S 





2'S 


1 


2 '2 


I'O 


•f'9 


1877 


1 


2'5 


2 


2 - 3 





2 - 2 





2'0 


1 


I- 3 





O'l 





°'3 





2'0 


1 


27 


1 


2 '4 


1 


2 -4 





2 


0'6 


i'8 


1878 


3 


2'5 


1 


2 '2 


1 


2 - 2 


2 


2'0 





I '2 





O'l 





°"3 


1 


I '9 





2'S 





2 '3 





2 '3 


1 


2'0 


0'8 


i'8 


1879 





2-4 


1 


2 - 2 


3 


2 - 2 


1 


2'0 





1*2 





O'l 





°'3 





i'8 





2 '4 





2 '2 


1 


2 '2 


2 


2'0 


0-7 


i'7 


1880 





2 '3 





2'0 


1 


2'I 


1 


1-9 


1 


I'l 





O'l 





°'3 


2 


i'8 





2 '3 


2 


2'I 


2 


2 '2 


2 


2'0 


9 


i'7 


1881 


1 


2 '2 


2 


2'0 


1 


2'I 


1 


I '9 





I 'I 





O'l 


1 


°'3 


1 


i'8 


2 


2 '3 


1 


2 P I 


3 


2 '2 


2 


2'0 


1-3 


1 '7 


1882 


2 


22 


1 


2'0 


2 


2'I 


2 


i-9 





I'O 





O'l 





°'3 





17 


3 


2 '3 


2 


2"I 


3 


2'3 


3 


2'0 


1-5 


i'7 


1883 


2 


2 '2 


2 


2'0 


2 


2'I 


1 


i-8 





I'O 





O'l 





o'3 





i'6 




2 2 


2 


2'I 


2 


2 '3 


1 


2'0 


1-1 


i'6 


1884 





2'I 


1 


2'0 


1 


2'0 


2 


i-8 


1 


I'O 


1 


O'l 





°'3 





16 




2 '2 


2 


2 P I 


1 


2'2 


2 


2'0 


I'O 


i'6 


1885 





2 


1 


I- 9 


1 


2'0 


1 


r8 


1 


I'O 





O'l 


1 


°"3 





1 '5 




2 '2 





2'0 


1 


2 '2 


2 


2'0 


0'8 


i'6 


1886 


1 


2'0 


1 


I '9 


1 


2'0 


1 


i-8 


2 


I'O 


1 


O'l 


1 


°'3 


1 


!'5 




2'I 


2 


2'0 


2 


21 


1 


2'0 


1-2 


i'6 


1887 


2 


2'0 


2 


I- 9 


2 


2'0 


1 


i -8 





I'O 





O'l 





°'3 


1 


1 '5 




21 


1 


2'0 


1 


2'I 


2 


2'0 


1-1 


1 -6 



MEAN SCOTTISH METEOROLOGY. 



215 



Table XX.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Aurora. — Number op Stations at which Aurora was observed. 





Jan. 


Feb. 


March. 


April. 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Mean Month 

of Observed 

Quantities 

in each 

Year. 


Successive 
Means of 
the Accu- 
mulating 
Years. 


Nights 

X 
Stations. 


Ace. 

Mns. 

Ni. 

X 

Sta. 


Year. 
1 


»»., 


4n. 


3b. 


Ac. 
Un. 


»i 


Yc. 
In. 


>"•] 


Vc. 


3b. 


\c. 
Un. 


3b. j 


Un. 


3b., 


Vc. 
In. 


3b., 


Vc. 

In. 


3b., 


Ac. 

Un. 


Mn. 


3b. 


Ac. 
«n. 


Ob. 


Ac. 
Mn. 


1856 


























































1857 


























































1858 


























































1859 


























































1860 


7 




28 




19 




16 









3 









6 




12 




6 




10 




20 




11 




19-8 




1861 


18 




26 




10 




11 




1 









1 




2 




7 




17 




12 




18 




10 




24 




1862 


6 


12 


13 


27 


7 


14 


9 


14 


4 








2 








5 


4 


13 


10 


18 


12 


11 


II 


19 


19 


9 


IO 


17-1 


21 - 9 


1863 


16 


IO 


13 


22 


10 


12 


11 


12 


3 


2 





I 








3 


4 


12 


11 


11 


14 


22 


11 


8 


19 


9 


IO 


16-2 


20-3 


1864 


7 


12 

ii 


13 


20 
18 


12 


12 
12 


10 


12 
11 


4 


2 
2 


1 


I 

I 


1 







12 


4 
6 


12 


II 

ir 


11 


13 
13 


11 


14 
13 


8 


16 
iS 


8 


IO 

9 


15-2 


19-3 

i8-5 


1865 


25 




26 




25 




8 




1 









1 




8 




12 




27 




9 




5 




12 




27-6 




1866 


5 


13 


26 


20 


5 


14 


10 


11 


■2 


2 





I 


2 





2 


6 


11 


11 


12 


IS 


16 


12 


15 


13 


9 


IO 


21-6 


20 - o 


1867 


4 


12 


10 


21 


13 


13 


4 


11 


2 


2 





I 





I 


4 


5 


11 


11 


19 


15 


10 


13 


5 


13 


7 


IO 


14-7 


20 '2 


1868 


13 


11 


8 


19 


13 


1 3 


15 


10 


4 


2 











I 


10 


5 


7 


11 


24 


iS 


9 


13 


6 


12 


9 


9 


17-1 


I9-S 


1869 


8 


11 
11 


12 


18 
18 


19 


13 
13 


19 


10 
11 


15 


2 

4 












I 



5 


6 
6 


11 


11 
11 


27 


16 
17 


13 


12 
12 


12 


12 
12 


12 


9 
10 


24-0 


i9"3 
197 


1870 


14 




15 




22 




7 




2 









1 




8 




29 




36 




14 




14 




14 




36-4 




1871 


4 


11 


9 


17 


7 


14 


18 


11 


2 


3 











I 


14 


6 


13 


12 


13 


19 


33 


12 


8 


12 


10 


10 


19 


21 - 2 


1872 


7 


11 


39 


17 


8 


14 


23 


12 


1 


3 








1 





17 


7 


18 


12 


16 


18 


9 


14 


10 


12 


12 


10 


25-2 


2I"I 


1873 


11 


10 


9 


18 


7 


13 


27 


12 





3 











I 


4 


7 


9 


13 


S 


18 


12 


14 


4 


II 


8 


10 


12-8 


21 - 4 


1874 


11 


10 
IO 


18 


18 
18 


7 


13 
12 


4 


13 
13 


2 


2 

3 

















2 


7 

7 


9 


*3 

12 


14 


18 

17 


2 


14 

15 


5 


II 
IO 


6 


10 

IO 


9-6 


20 -8 
20 "O 


1875 


6 




4 




4 




S 




1 














4 




S 




13 




2 




1 




4 




4-8 




1876 


5 


10 


7 


17 


3 


12 





12 





3 














1 


7 


1 


12 


1 


17 





12 


3 


IO 


2 


9 


2-0 


19-1 


1877 


3 


IO 


1 


16 





II 





12 


3 


3 

















6 


3 


11 


1 


16 


3 


12 





9 


1 


9 


0-6 


18-1 


1878 


1 


9 


1 


iS 


2 


II 


1 


11 





3 














1 


6 





11 





iS 





II 


1 


9 


1 


9 


0-8 


17-1 


1879 





9 
9 


1 


15 
14 


3 


IO 
IO 


1 


11 
10 





2 

2 



















6 

5 





IO 

10 





14 
14 


4 


10 
10 


4 


9 
8 


1 


8 
8 


0-7 


l6'2 

IS '5 


1880 












11 




1 




1 














12 









9 




13 




2 




2 




1-8 




1881 


•22 


8 


3 


13 


5 


IO 


3 


10 





2 








1 





1 


6 


3 


9 


3 


13 


5 


10 


3 


8 


4 


7 


5-2 


14-8 


1882 


4 


9 


6 


13 


2 


IO 


2 


9 





2 

















6 


2 


9 


11 


13 


19 


10 


3 


8 


4 


7 


6 


14 '4 


1883 


6 


9 


16 


13 


12 


9 


7 


9 





2 

















5 


3 


9 


4 


13 


6 


10 


3 


8 


5 


7 


5-5 


i4 - o 


1884 





8 
8 


4 


13 

12 


3 


9 
9 


6 


9 
9 


3 


2 
2 


1 

















5 

s 


5 


9 
8 


2 


13 

12 


1 


10 

10 


4 


7 
7 


2 


7 
7 


2-0 


137 
13-2 


1885 







4 




14 




1 




1 









1 









4 









3 




6 




3 




2-4 




1886 


16 


8 


3 


12 


17 


9 


3 


9 


3 


2 


1 





4 





2 


s 


1 


8 


7 


12 


S 


10 


6 


7 


6 


7 


7-2 


12-8 


1887 


8 


8 
8 


6 


12 
II 


5 


10 
9 


1 


8 
8 





2 
2 
















3 


5 
s 


3 


8 
8 


5 


II 
II 


4 


10 

9 


6 


7 
7 


3 


7 
7 


3 3 


12 - 6 
12.2 



216 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXI.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Maxima op Temperature. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


JuJy. 


Obsd. 


Sueces. 
Ileus. 


Obsd. 


Sueces. 
Means. 


Obsd. 


Sueces. 
Means. 


Obsd. 


Sueces. 
Means. 


Obsd. 


Sueces. 

Means. 


Obsd. 


Sueces. 

Means. 


Obsd. 


Sueces. 
Means. 


1856 


37 9 




44-0 




46-0 




509 




53-8 




60-5 




64-8 




1857 


39-8 


3 8-8 


44-3 


44 '2 


44-0 


45'° 


487 


49-8 


57-0 


55 '4 


66-0 


63-2 


65-0 


64-9 


1858 


44 


40 '6 


41-2 


43 ' 2 


45-5 


45 '2 


51-4 


5°'3 


56-9 


55 '9 


671 


°4'5 


63-4 


°4'4 


1859 


44-4 


4i '5 


45-4 


437 


48-4 


46 'o 


487 


49 "9 


617 


57 '4 


64-6 


64-6 


66-2 


64-8 


1860 


39-5 


41-1 


39-4 


42-9 


44-2 


45 '6 


48-9 


497 


577 


57 - 4 


59-6 


63-6 


64-5 


64-8 


1861 


40-4 


41/0 


44-1 


43' 1 


46-8 


45-8 


52-4 


50 -2 


56-9 


57 '3 


64-0 


63-6 


63-6 


64-6 


1862 


42-0 


41 'I 


44-4 


43 "3 


42-4 


45 '3 


51-4 


5° '3 


581 


57 '4 


587 


62*9 


60-4 


64 


1863 


42-9 


41-4 


46-6 


437 


48-5 


457 


51-1 


5o - 4 


55-6 


57 '2 


60-6 


62-6 


64-5 


64 - o 


1864 


40-8 


4i "3 


391 


43 "2 


43-0 


45 '4 


53 3 


50-8 


58-0 


57 "3 


60-2 


62 - 4 


641 


64'i 


1865 


39-2 


41-1 


38-5 


427 


427 


45 - 2 


54-5 


5 1 ' 1 


57-9 


57 - 4 


657 


627 


66-3 


64 '3 


1866 


43-8 


4i "3 


40-6 


42 "5 


437 


45 "o 


50-6 


5" 


56-9 


57 "3 


64-0 


62-8 


63-9 


64 '3 


1867 


36-6 


40-9 


46 '2 


42-8 


41-9 


44-8 


611 


5i 'i 


53-6 


57 "O 


61-3 


627 


61-2 


64 - o 


1868 


42-0 


41 'O 


46 6 


43' 1 


48-8 


45 '1 


52-4 


5 1 ' 2 


58-8 


57'i 


63-8 


62-8 


69-5 


64-4 


1869 


44-4 


4i "3 


46-8 


43*4 


43-8 


45 "o 


54-8 


5i "4 


52-5 


56-8 


61-0 


62-6 


67-2 


64-6 


1870 


40-0 


41*2 


39-8 


43'i 


457 


45'° 


547 


5i7 


57-6 


56 '9 


63-0 


627 


67-4 


64-8 


1871 


38-2 


41 - o 


45-1 


43 '3 


49-0 


45 "3 


491 


5i '5 


591 


57 'o 


610 


62-6 


647 


64-8 


1872 


43-2 


41-1 


45-6 


43 '4 


47-2 


45 "4 


515 


51 '5 


54-2 


S 6-8 


62-0 


62-5 


667 


64-9 


1873 


43-7 


41 '3 


41-0 


43 '3 


45-3 


45 '4 


52-2 


51 '5 


54-2 


567 


637 


62-6 


661 


65-0 


1874 


45-5 


41 "5 


44-4 


43 "3 


49 3 


45 '6 


54-4 


Si7 


54-2 


56-6 


64-2 


627 


67 - 2 


65-1 


1875 


44-5 


41 '6 


41-1 


43' 2 


45-8 


45" 6 


551 


5i '9 


59 3 


567 


62-0 


62-6 


65-5 


65-i 


1876 


44 '0 


41-8 


41-8 


43 -1 


42-9 


45 '5 


50-3 


51-8 


57-2 


567 


63-8 


627 


66 1 


65-2 


1877 


42-4 


41-8 


44-8 


43 ' 2 


44-6 


45 "4 


47-4 


5i-6 


52-9 


56-6 


62-5 


627 


62-5 


65-0 


1878 


42-8 


41 "8 


46-3 


43*4 


46-5 


45 '5 


52-5 


5i-6 


57-5 


56-6 


637 


627 


67-5 


65 '2 


1879 


36-2 


41 '6 


38-8 


43 '2 


43-0 


45 '4 


47-2 


Si '4 


54-3 


56-5 


60 


62-6 


60-8 


65-0 


1880 


41-6 


41 '6 


46-7 


43 '3 


48-5 


45 '5 


517 


5i"5 


57-2 


56-5 


63-5 


627 


63-9 


64-9 


1881 


34-5 


4i '3 


39-0 


43' 1 


43-5 


45 '4 


501 


5 I- 4 


59-4 


56-6 


611 


62-6 


637 


64-9 


1882 


45-9 


4i'S 


47-5 


43 '3 


49-2 


45'6 


49-9 


5i '3 


58-9 


567 


61-4 


62-6 


64-6 


64-9 


1883 


42-8 


41 "5 


45-3 


43 '4 


42-2 


45 "4 


52-0 


5i '4 


55-6 


5 6 7 


61-6 


62-5 


631 


64-8 


1884 


44-8 


416 


44-1 


43 "4 


46-8 


45 '5 


50-6 


5i '3 


56 '6 


567 


62-2 


62-5 


64-5 


64-8 


1885 


40-2 


41 '6 


44-0 


43 "4 


45-3 


45 '5 


51-2 


5i "3 


52-3 


56-5 


61-9 


62-5 


66-2 


64-8 


1886 


39 


4I-S 


39-2 


43 '3 


42-9 


45 "4 


50-5 


5i '3 


54-2 


56-5 


611 


62*4 


64-2 


64-8 


1887 


42-0 


4i - S 


45-4 


43 '4 


45-4 


45 '4 


50-2 


Si '3 


571 


56-5 


671 


62-6 


67-5 


64-9 



MEAN SCOTTISH METEOROLOGY. 



217 



Table XXI. continued.— SCOTTISH COUNTEY AND TOWN STATIONS, METEOEOLOGY OF. 

Mean Maxima op Temperature. 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 

Quantities 

in each Year. 


Means of the 

Accumulating 

Years. 


Year 

repeated. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


64-4 




57-5 




54-2 




44-7 




42-5 




51-8 




1856 


67-0 




62-5 




55-3 




48-3 




49-1 




53-9 




1857 


65-9 


657 


618 


60 "O 


511 


54-8 


44-2 


46-5 


44-1 


45'8 


53-0 


52-8 


1858 


65-2 


6 S -8 
6 S -6 


591 


60 -6 ; 
60'2 


51-8 


53'5 
53'i ; 


44-6 


457 
45 '4 


38-4 


45 '2 
43 '5 


53-2 


52-9 
53 '0 


1859 


60-8 




57-1 




51-4 




43-1 




38-1 




50-4 




1860 


62-9 


647 


59-2 


59 '6 


55-3 


52-8 


43-9 


45 "o 


42-8 


42-4 


52-7 


52-5 


1861 


62-3 


64-4 


60-4 


59 '5 


53-5 


53 '2 


42-6 


44-8 


46-2 


42 '5 


51-9 


52-5 


1862 


62-7 


64*1 


56-2 


597 


52-1 


53'2 


48-0 


44 '5 


45-7 


43 'o 


52-9 


52-4 


1863 


62-4 


63 '9 
637 


59-3 


59 '2 
59 '2 


51-4 


S3" 1 

52-9 


46-2 


44'9 
45'i 


43-2 


43 '4 
43 '3 


51-8 


52-5 
52 - 4 


1864 


627 




66-0 




52-1 




46-8 




47-1 




53-3 




1865 


61-4 


63-6 


57-8 


S9'9 


54-2 


52-8 


46-2 


45 '2 


45-4 


437 


52-4 


52-5 


1866 


64-2 


63 '4 


59-2 


597 


52-4 


52-9 


46-8 


45 '3 


43-4 


43 '9 


51-5 


52-5 


1867 


65-5 


63 \5 


59-5 


597 


51-2 


52'9 


43-8 


45 "4 


45-0 


43-8 


53-9 


52'4 


1868 


64-3 


63-6 
637 


59-7 


597 
597 


52-9 


52-8 
52-8 


45-6 


45 "3 
45 '3 


39-9 


43 '9 
43 "6 


527 


52-5 
52-5 


1869 


66-9 




614 




52-7 




44-5 




38-3 




527 




1870 


66-8 


63 '9 


58-8 


S9'8 


53 2 


52-8 


43-5 


45 '3 


43-0 


43 '3 


52-6 


52-S 


1871 


63-5 


64" 1 


57-1 


597 


51-4 


52-8 


46-1 


45 '2 


42-5 


43 '3 


52-6 


52"5 


1872 


63-0 


64'i 


58-6 


59 '6 


50-7 


527 


46-3 


45 '2 


47-3 


43 '2 


52-7 


52-5 


1873 


63-2 


64 'O 
64 '0 


59-4 


59 - 5 
59 '5 i 


53-1 


52-6 
52-6 


45-9 


45 '3 
45 '3 


36-6 


43 '4 
43'i 


53-1 


52-6 
52-6 


1874 


64-9 




61-6 




52-1 




44 3 




43-5 




53-3 




1875 


66-2 


64 - o 


58-0 


59 '6 ! 


54-6 


52 -6 


45-5 


45 '3 


437 


43 'i 


52-9 


52-6 


1876 


61-2 


64T 


57-8 


59 '5 


52-9 


527 


47-5 


45 "3 


44-0 


43'i 


51-7 


52 -6 


1877 


65-8 


64 "o 


60-9 


59 \5 


54-3 


527 


43-0 


45 "4 


36-1 


43 '2 


531 


52 '6 


1878 


62-6 


64"! 
64-0 


58-3 


59'5 
59'5 


53-2 


52-8 
52-8 


457 


45 '3 
45 '3 


40-5 


42-9 
42-8 


50-0 


S2'6 
52-5 


1879 


67-5 




63 '0 




49-5 




44-9 




41-8 




53-3 




1880 


60-5 


64"i 


58-8 


59'6 


50-7 


527 


50-6 


45 "3 


43-3 


427 


51-3 


52-5 


1881 


64-9 


64^0 


59-1 


59 '6 


53-8 


52-6 


44-6 


45 '5 


38-6 


42-8 


53-2 


52-5 


1882 


63-4 


64'o 


59-8 


59 '6 


53-1 


S 2 '6 


45-8 


45'5 


44-5 


42 '6 


52-4 


52-5 


1883 


66 5 


64 - o 
64 - i 


61-7 


59 '6 
59 '6 


53-1 


52-6 
52-6 


45-8 


45 '5 
45 '5 


41-4 


427 
42 "6 


53-2 


52-5 
52 "5 


1884 


61 '2 




58-0 




48-2 




45-4 




43-4 




51-4 




1885 


63-5 


64 - o 


59-5 


59 '6 


54-9 


52-5 


48-1 


45 - 5 


38-3 


42 - 6 


51-3 


52-5 


1886 


64-8 


64 'O 
64 - o 


58-6 


59 '6 
59 - 6 


50-6 


52-6 
52-5 


44.4 


45 '6 
45 '6 


41-2 


42-5 
42'5 


52-9 


5 2< 5 
52-5 


1887 



VOL. XXXV. PART 3. 



2 K 



218 



PROFESSOR C. PTAZZI SMYTH ON 



Table XXII.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Minima of Temperature. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


July. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


1856 


30-7 




35-2 




32-8 




37-7 




39-6 




461 




48-0 




1867 


31 '6 




34-3 




34-4 




36-7 




42-6 




48-8 




51-0 




1858 


34-6 


31-2 


30-4 


34-8 


33-5 


33'6 


36-2 


37 '2 


42-1 


41 -i 


507 


47 '4 


48-6 


49 "5 


1859 


34-8 


32 '3 
32 9 


35-6 


33'3 
33'9 


37 6 


33'° 
34 "6 


35-1 


36-9 
36-4 


42-1 


41 "4 
41 "6 


48-6 


48-S 
48-6 


51-8 


49 '2 
49-8 


1860 


31-5 




28-6 




32-6 




34-1 




427 




46-4 




50-1 




1861 


322 


32-6 


34-9 


32-8 


35-4 


34 '2 


38-4 


36-0 


41-3 


41-8 


50-4 


48-1 


50-0 


49'9 


1862 


34-8 


32-6 


35-8 


33'2 


33-2 


34'4 


37-8 


36 "4 


44-1 


4i7 


46-1 


48-S 


47-2 


49 '9 


1863 


34-1 


32-9 


35-8 


33'S 


37-3 


34 '2 


377 


36-6 


41-6 


42'! 


47-4 


48-2 


477 


49 'S 


1864 


316 


33 '0 
32-9 


27-9 


33'8 
33 '2 


32-0 


34 '6 
34*3 


38-9 


3 6 7 
37 '° 


42-0 


42 - o 
42 "O 


46-6 


48-1 
47 '9 


49-3 


49 '3 

49 '3 


1865 


30-0 




29-3 




31-9 




38-5 




43-9 




48-5 




50-5 




1866 


35 


32 -6 


32-8 


32-8 


32-3 


34 "i 


37'4 


37"i 


38-9 


42 - 2 


48-2 


48-0 


49-9 


49 "4 


1867 


27-0 


32-8 


36-6 


32-8 


30-5 


33 "9 


39-5 


37'i 


41-4 


41-9 


47-3 


48-0 


48-4 


49 "5 


1868 


33-0 


3 2 '3 


36 6 


33"i 


36-8 


33'° 


39-6 


37 3 


44-0 


41 '9 


47-4 


47 '9 


51-3 


49 '4 


1869 


36-4 


32 '4 

32 7 


37-0 


33 '4 
33 ' 6 


31-8 


33 '9 
337 


39-0 


37 '5 
37 '6 


377 


42 'O 

417 


45-2 


47 '9 
477 


51-4 


49 '5 
497 


1870 


31-8 




306 




33-3 




39-1 




43-4 




48-2 




51-8 




1871 


29-4 


32 '6 


36 9 


33-4 


36 2 


337 


35-9 


377 


41-5 


41-8 


45-8 


477 


507 


49-8 


1872 


34-8 


32 '4 


36-8 


33 '6 


36-4 


33'S 


38-9 


37 * 


40-6 


41*8 


48-2 


47 '6 


51-9 


49'9 


1873 


34-7 


32 '5 


29-8 


33'8 


34-1 


34'° 


37-4 


377 


39-6 


417 


48-1 


47-6 


50-9 


50-0 


1874 


35-5 


327 
328 


33-2 


33 "6 
33 '6 


37-3 


34 '° 
34"2 


39-0 


377 
377 


40-0 


41 "6 

4i '5 


45-4 


477 

47-5 


51-6 


50-0 
5o-i 


1875 


34 9 




31-5 




342 




37-9 




44-1 




46-0 




487 




1876 


34-4 


329 


32-0 


33 "5 


32-3 


34"2 


37-1 


377 


40-6 


417 


46-2 


47 '5 


50-4 


50-0 


1877 


32-8 


33 'o 


34-2 


33 '4 


32-2 


34'i 


35-4 


377 


38-9 


41 - 6 


477 


47 '4 


50-1 


50-1 


1878 


33-2 


33 "o 


36-7 


33 '4 


34-1 


34 "o 


38-5 


37 '6 


43-1 


41 - S 


47-3 


47 '4 


51 '5 


50-1 


1879 


25-8 


33 'o 
327 


29-2 


33 '6 
33 "4 


32-0 


34 '0 
33 '9 


34-8 


37 '6 
37 '5 


38-1 


41 '6 
41-4 


46-4 


47'4 
47 "4 


48-8 


50-1 
5°'i 


1880 


32-0 




367 




33-9 




377 




40-8 




46-3 




49-5 




1881 


21-9 


327 


29-8 


33'S 


30-7 


33 "9 


34-3 


37 '5 


41-4 


41-4 


447 


47 - 3 


497 


50 -o 


1882 


36-7 


32-2 


37-1 


33 '4 


36-8 


33-8 


36-3 


37 '4 


40-5 


41 '4 


45-6 


47 "2 


50-0 


50-0 


1883 


33-8 


32 - 4 


35-3 


33 "S 


29-8 


33 "9 


37-2 


37 - 4 


40-0 


41 "4 


45-4 


47 "2 


487 


5°'° 


1884 


35-8 


32'S 
32-6 


34-3 


33° 
33"° 


353 


33'S 
33'S 


36-0 


37 '4 
37 '3 


40-5 


4i '3 
4i "3 


46-2 


47'i 
47 'i 


50-1 


50 'O 
50-0 


1885 


31-6 




32-9 




32 1 




36-6 




381 




45-3 




487 




1886 


291 


32-6 


297 


33 '° 


31-7 


33 '8 


357 


37 '3 


397 


41*2 


447 


47 '0 


48-6 


5° 'o 


1887 


330 


32 '5 
32 - S 


34-1 


33 '5 
33 "5 


319 


337 
337 


34-3 


37 ' 2 
37'* 


407 


41 '2 

41-1 


48-1 


46-9 
47'° 


51-1 


49 '9 
50-0 



MEAN SCOTTISH METEOROLOGY. 



219 



Table XXIL continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Mean Minima of Temperature. 





August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 


























of Observed 
Quantities in 
each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 




Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 




49-8 




44-3 




43-4 




347 




33-3 




39-6 




1856 




53'0 




497 




43-9 




39-1 




407 




42-2 




1857 




49-9 


5i '4 


47-2 


47-0 


387 


43 " 6 


34 6 


3^-9 


35-7 


37 O 


40-2 


4°'9 


1858 




50-4 


5°'9 
5 o-8 


45-5 


47 'i 
467 


39-8 


42 'o 
41 "4 


34-2 


36-1 
35 '6 


29-6 


36-6 
34-8 


40-4 


407 
40 '6 


1859 




48-0 




43-3 




40-6 




35-1 




30-1 




38-6 




1860 




519 


50 '2 


48-2 


46 - o 


437 


4i '3 


33-1 


35"S 


33-2 


33 '9 


41-1 


40 "2 


1861 




497 


5° "5 


46-4 


46-4 


407 


417 


31-6 


3S"i 


37-4 


33-8 


40-4 


40-4 


1862 




487 


5° - 4 


44-0 


46-4 


41-5 


41-5 


38-2 


34 '6 


35-9 


34 '3 


40-8 


4° '4 


1863 




46-4 


50-2 
49-8 


45-5 


46*1 
46 '0 


40-2 


41-5 
41-4 


35-6 


3S*i 

35'i 


35-6 


34' 5 
34"6 


39-3 


40-4 
4° '3 


1864 




49-5 




50-0 




39-9 




36-0 




387 




40-6 




1865 




48 '6 


497 


45-0 


46-4 


43 '0 


41-2 


36-2 


35'2 


35-8 


35 "o 


40-3 


4° '3 


1866 




50-6 


49 "6 


47-6 


46 - 3 


40-4 


41 '4 


36-4 


35 '3 


34-2 


35'i 


40-0 


40 '3 


1867 




51-5 


497 


46-9 


46-4 


38-4 


4i "3 


34-6 


35 '4 


36-2 


35'° 


41-4 


4°'3 


1868 




47-9 


49-8 
497 


477 


46-4 
46-5 


417 


41-1 
41 -i 


35 2 


35'3 
35 '3 


29-9 


35'i 
347 


40-1 


40-4 
40-4 


1869 




49-1 




45-8 




39-9 




337 




28-7 




39-6 




1870 




51-0 


497 


45-6 


46-S 


41-2 


41-1 


337 


35'2 


33-0 


34 '3 


401 


4°'3 


1871 




49-5 


49-8 


45-9 


46-4 


40-2 


4 ri 


36-5 


35'i 


34-1 


34 "2 


41-2 


4° - 3 


1872 




49-8 


497 


44-2 


46-4 


37-9 


41 - o 


36-1 


35 '2 


377 


34'2 


40-0 i 


4°'3 


1873 




48-6 


497 
497 


46-2 


46 - 3 
46 - 3 


39-9 


40-8 
40 '8 


36-3 


35 '3 
35 '3 


25-2 


34"4 
33'9 


39-8 


4° "3 
4° '3 


1874 




513 




47-2 




41-9 




34-1 




34-3 




40-5 j 




1875 




49-4 


49-8 


45-6 


46'3 


45-0 


40-8 


35-9 


35"2 


36 3 


34 "o 


40-4 


4° '3 


1876 




49-0 


497 


43-2 


4 6 '3 


40-5 


41 


37-5 


35"3 


34-6 


34'i 


397 


40 '3 


1877 




51-4 


497 


477 


46 - i 


43-5 


41 "o 


33-0 


35 '4 


25-3 


34"i 


40-4 


4°'3 


1878 




49-4 


49-8 
49-8 


447 


46 - 2 
46T 


38-8 


41 -i 
41 'O 


35-3 


35 '3 ; 

35 '3 


28-9 


337 
33 "5 


37-7 


4°'3 

40 "2 


1879 




51-3 




47-4 




35-3 




32-1 




31-4 




395 




1880 




46-5 


49-8 


46-0 


46 '2 


38-9 


40-8 


39-4 


35 '2 


33-3 


33"4 


38-0 


4C2 


1881 




497 


497 


44-5 


46-2 


42-2 


407 


33-6 


35 "3 


28-6 


33 "4 


401 


40-1 


1882 




49-0 


497 


45-8 


46 - I 


397 


40-8 


35-0 


35'3 


34-3 


33 '2 


39-5 


40-1 


1883 




50-3 


497 
497 


467 


46-1 
46-1 


407 


407 
407 


34-6 


35'2 
35'2 


32-0 


33 '3 
33 -2 


40-2 


40- 1 
40-1 ; 


1884 




45 9 




43-6 




36-6 




35-2 




331 




38-3 




1885 




48-9 


49 -6 


44-9 


46-0 


44-1 


40 - 6 


37-5 


35 '2 


277 


33 ' 2 


38-5 


40 '0 


1886 




48-0 


49 -6 
49 -6 


44-5 


46 "O 
46 'O 


37-5 


407 
40-6 


34-8 


35 '3 
35 '3 


31-1 


33"i 
33'° , 


391 


39 '9 
39 - 9 


1887 



•220 



PROFESSOR C. PIAZZI SMYTH ON 



Table XX III.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Accumulated Rainfall. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


1856 


2-38 




5-68 




5-94 




8-38 




11-00 




1471 




1857 


2-77 




4-31 




7-25 




9-63 




11-29 




14-08 




1858 


2-98 


2-58 


4-11 


5-00 


6-06 


6-6o 


7-92 


9-00 


10-73 


11-14 


13-09 


14-40 


1859 


4-21 


271 

3-08 


7-59 


470 

5 "42 


11-77 


6*42 
776 


14-97 


8-64 

IO - 22 


15-26 


1 1 "or 
12-07 


17-30 


13-96 

14-80 


1860 


4-56 




7-25 




10-77 




11-95 




14-13 




18-47 




1861 


3-09 


3-38 


641 


579 


U-51 


8-36 


12-55 


i°'57 


14-12 


12-48 


16-47 


15 '53 


1862 


5-32 


3 '33 


7-20 


S'8g 


10-83 


8-88 


13-82 


10-90 


17-71 


1276 


2170 


i5 - 69 


1863 


6-20 


3 '62 


8-60 


6-o8 


10-68 


9-16 


13-95 


11-32 


16-29 


i3'46 


19-53 


16-55 


1864 


2-84 


3 '94 
3-82 


6-59 


6-39 
6-42 


10-55 


9 '35 
9-48 


12-12 


11-65 
11 70 


14-10 


13-82 
i3'85 


16-67 


16-92 
16-89 


1865 


3-73 




6-64 




8-69 




9-63 




12-99 




1374 




1866 


5-31 


3-81 


9-82 


6 '44 


12-97 


9-40 


14-65 


11-49 


16-01 


1376 


17-86 


16-58 


1867 


4-74 


3 '94 


7-83 


6'75 


10-09 


973 


14-52 


11 78 


17-35 


i3'97 


19-46 


16-69 


1868 


5-53 


4 - oi 


10-28 


6-84 


14-50 


976 


17-81 


I2 - OI 


20-32 


i4'25 


21-46 


16-92 


1869 


4-85 


4'i3 
4-18 


8 '90 


7'io 
7 '23 


10-23 


IO"I2 
IO-I3 


12-22 


12-45 

12-44 


13-59 


14-72 
14-64 


1574 


17-27 
17-16 


1870 


3-08 




6-97 




8-21 




9-79 




12-40 




14-31 




1871 


2-74 


4-11 


7-14 


7 - 2I 


9-64 


io - oo 


13-72 


12-26 


14-84 


14-49 


16-91 


16-97 


1872 


6-48 


4 '02 


10-76 


7'2I 


14-02 


9-98 


16-16 


12-35 


19-48 


i4'5i 


24-64 


16-97 


1873 


5-37 


4T7 


6-82 


7-42 


9-14 


IO"22 


9-84 


12-58 


12-53 


14-80 


14-27 


17-42 


1874 


4-02 


4'23 

4 - 22 


5-73 


7'38 

7 '3° 


8-55 


IO'l6 
IC07 


10-82 


12-42 

12-34 


12-64 


14-67 
i4'57 


14-06 


17-24 

17-08 


1875 


5 '63 




7-35 




9-03 




10-44 




12-47 




15-61 




1876 


2-84 


4'29 


7-17 


7 '3° 


12-27 


IO - 02 


15-38 


12-24 


16-29 


14-46 


19-41 


17-00 


1877 


6-96 


4 - 22 


11-08 


7-29 


13-66 


IO-I3 


16-62 


12-39 


19-37 


i4'55 


23-09 


17-12 


1878 


4-01 


4'35 


5-93 


7-46 


8-02 


IO-29 


9-73 


12-59 


13-12 


i4'77 


15-90 


i7'39 


1879 


1-84 


4 '33 
4 '23 


4-36 


7-40 
7-27 


7-56 


IO-I9 

10 'o8 


9-45 


12-46 
12-34 


11-75 


14-70 
I4'S7 


15-99 


17 '33 
1727 


1880 


2-02 




6-00 




8-32 




11-69 




12-89 




14-98 




1881 


1-30 


4-14 


5-09 


7 "22 


8-58 


IO'OI 


9-74 


12-31 


12-22 


H'51 


15-45 


17-18 


1882 


3-41 


4'°3 


6-61 


7'H 


10-78 


9-96 


13-87 


I2'2I 


16-03 


14-42 


19-71 


17-11 


1883 


4 '48 


4'oi 


8-62 


7"I2 


10-98 


9 '99 


12-86 


I2'27 


14-70 


14-48 


17-04 


17-21 


1884 


5-80 


4 - 02 

4 "°9 


9-64 


7-17 
7-26 


12-88 


IO'02 
IO - I2 


14-19 


I2'29 
12-36 


17-20 


14-49 
I4'58 


18-07 


17-20 
17 '23 


1885 


2-93 




7-28 




9-81 




12-37 




15-59 




17-04 




1886 


4-42 


4 '°5 


6-23 


7*26 


9-37 


IOII 


11-35 


12-36 


14-92 


14-61 


16-50 


17-22 


1887 


3-25 


4 - o6 
4 '°3 


. 5-71 


7 '23 
7-17 


7-59 


IC09 
IO'OO 


9-64 


12-33 
12-24 


11-03 


i4'63 
i4'5i 


11-99 


17-21 
17-04 



MEAN SCOTTISH METEOROLOGY. 



221 



Table XXIII. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Accumulated Rainfall. 



July. 


August, 


September. 


October. 


November. 


December. 


Year 
repeated. 


























Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 




17-26 




20-72 




25-36 




2679 




28-91 




33-00 




1856 


16-25 




18-12 




21-94 




24-30 




27-19 




30-56 




1857 


17-40 


16-76 


20-01 


19-42 


22-81 


23 - 65 


27-53 


25 '54 


29-91 


28-05 


33-91 


3178 


1858 


20-06 


16-97 
1774 


22-33 


19-62 
20-30 


25-54 


23 '37 
23-91 


30-14 


26-21 
27-19 


33-51 


28-67 
29-88 


37-17 


32'49 
33'66 


1859 


20-29 




24-08 




26-00 




31-14 




33-97 




37-88 




1860 


20-41 


18-25 


26-85 


21-05 


32-12 


24 '33 


35-46 


27-98 


42-09 


3070 


45-07 


34'5o 


1861 


25-57 


18-61 


28-92 


22'02 


31-36 


25-63 


37-68 


29-23 


40-09 


32-60 


45-29 


36-26 


1862 


20-25 


19-61 


24-75 


23-00 


29-47 


26-45 


33-58 


3° '43 


37-10 


33'67 


42-11 


37 '55 


1863 


19-04 


19-69 
19-61 


20-70 


23-22 

22 -94 


25-31 


26-82 
26-66 


30-78 


30'83 
30-82 


34-87 


34-10 
34-18 


38-58 


38-12 
38-17 


1864 


16-83 




20-72 




21-86 




26-97 




30-26 




33-91 




1865 


21-00 


19 '34 


24-99 


22-72 


29-33 


26-18 


32-19 


3°'44 


36-12 


3379 


41-41 


3775 


1866 


23-84 


19-49 


26-66 


22-93 


29-83 


26-46 


34-12 


30-60 


35-37 


34-00 


38-52 


38-08 


1867 


22-16 


19-85 


27-34 


23-24 


30-68 


2674 


34-39 


30-89 


37-01 


34'i2 


43-03 


38-12 


1868 


17-36 


20 '03 
19-84 


18-68 


23 '55 
23-20 


24-60 


27-05 
26-87 


27-60 


31-16 
30-90 


31-88 


34'34 
34'i6 


36-54 


38'5o 
38-36 


1869 


16-19 




17-74 




21-06 




25-69 




28-27 




31-81 




1870 


21-07 


19 '59 


23-99 


22-84 


26-56 


26-48 


30-02 


3° '56 


33-43 


3377 


37-19 


37-92 


1871 


28-23 


19-69 


32-12 


22-91 


38-06 


26-49 


42-81 


30-52 


48-82 


3375 


54-15 


37-87 


1872 


18-84 


20-19 


23-05 


23 "45 


27-41 


27-17 


32-88 


31 '25 


36-20 


34 '64 


39-33 


38-83 


1873 


17-17 


20 - II 
19-96 


22-71 


23 '43 
23 "39 


26-89 


27-18 
27-17 


32-94 


3i '34 
3i '42 


37-43 


3472 

34'87 


40-17 


38-86 
38-93 


1874 


18-51 




21-48 




25-82 




30-54 




35-41 




39-08 




1875 


21-67 


19-89 


25-40 


23-30 


28-96 


27-10 


33-73 


3i'38 


37-31 


34-89 


44-88 


38-94 


1876 


27-40 


19-97 


33-75 


23-40 


35-87 


27-19 


41-19 


3i'49 


47-26 


35 - oi 


51-83 


39-22 


1877 


17-02 


20-31 


20-98 


23-87 


25-60 


27-58 


30-06 


3 I- 93 


33-27 


35'57 


36-28 


3979 


1878 


21-02 


20-17 
20'2O 


25-50 


2374 
23-82 


29-49 


27-50 

27'S8 


31-46 


3I-85 
3i'83 


33-73 


35'47 
35'39 


36-43 


39'64 
39'5i 


1879 


18-67 




19-53 




23-21 




25-74 




30-77 




34-73 




1880 


19-61 


20'14 


23-94 


23-64 


26-95 


27 '4i 


30-46 


31 '59 


35-67 


35-21 


39-54 


39 '3i 


1881 


24-38 


20'12 


27-09 


23-66 


30-72 


27'39 


34-34 


31 '55 


39-76 


35'23 


44-92 


39 '32 


1882 


20-82 


20-28 


24-93 


2378 


28-19 


27 '5 1 


32-23 


3 I-6 5 


36-82 


35 "39 


40-38 


39 '53 


1883 


22-81 


20-30 
20-38 


25-28 


23-82 
23-87 


28-00 


27 "54 
27 '55 


31-46 


31-67 

31-66 


34-86 


35 '45 
35 '42 


39-44 


39-56 
39 '56 


1884 


18.69 




21-39 




2671 




29-99 




32-53 




35-42 




1885 


19-89 


20-32 


21-95 


2378 


25-91 


27'5i 


29 90 


31 '59 


33-77 


35'3i 


37-93 


39 '42 


1886 


14-96 


20-32 
20-I5 


17-68 


2374 
23 '55 


21-51 


27-48 
27-29 


23-90 


3i'56 
31*32 


27-66 


35 '29 
35 '05 


30-96 


39'37 
39-12 


1887 



VOL. XXXV. PART 3. 



2 L 



222 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXIV.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 



Useful Plant-Growth Temperature in each Month being the Excess op Mean Temperature above 
42° "0 F. x into Number op Days in each Month (to even degrees only). 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


July. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Suoces. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 

Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


1856 


-239 




- 70 




- 81 




+ 69 




+ 146 




+ 339 




+ 446 




1857 


-195 




- 76 




- 87 




+ 21 




+242 




+ 462 




+ 496 




1858 


- 84 


-217 


-174 


- 73 


- 78 


- 84 


+ 54 


+ 45 


+ 232 


+ 194 


+507 


+ 400 


+434 


+ 47 1 


1859 


- 74 


-173 
-148 


- 42 


-107 
- 90 


+ 31 


- 82 

- 54 


- 3 


+ 48 
+ 35 


+ 307 


+ 207 
+ 232 


+ 438 


+436 
+ 436 


+527 


+459 

+ 476 


1860 


-202 




-232 




-112 




- 15 




+254 




+ 330 




+ 474 




1861 


-177 


-159 


- 70 


-119 


- 28 


- 65 


+102 


+ 25 


+ 220 


+ 236 


+ 456 


+ 415 


+459 


+475 


1862 


- 112 


-162 


- 53 


-in 


-130 


- 59 


+ 78 


+ 38 


+282 


+234 


+312 


+ 422 


+366 


+ 473 ' 


1863 


-108 


-155 


- 22 


-102 


+ 28 


- 69 


+ 72 


+ 44 


+205 


+ 240 


+360 


+ 406 


+ 437 


+ 457 


1864 


-180 


-149 
-152 


-246 


-92 
- 109 


-140 


- 57 

- 66 


+123 


+ 47 
+ 56 


+248 


+236 
+ 237 


+342 


+ 400 
+394 


+ 456 


+455 ; 
+455 


1865 


-229 




-227 




-146 




+135 




+276 




+453 




+508 




1866 


- 81 


-160 


-148 


-121 


-124 


- 74 


+ 60 


+ 64 


+183 


+ 241 


+ 423 


+400 


+ 462 


+460 


1867 


-316 


-153 


- 17 


-124 


-180 


- 79 


+ 99 


+ 63 


+ 170 


+ 236 


+369 


+402 


+397 


+460 


1868 


-140 


-166 


- 12 


-"5 


+ 25 


- 87 


+120 


+ 66 


+291 


+ 230 


+408 


+ 399 


+570 


+ 455 


1869 


- 50 


— 164 
-156 


- 3 


— 107 

- 99 


-130 


- 79 

- 82 


+147 


+ 7° 
+ 76 


+ 96 


+23S 
+225 


+333 


+ 400 
+395 


+ 536 


+ 464 
+469 


1870 


-189 




-190 




- 78 




+ 147 




+264 




+ 408 




+546 




1871 


-254 


-158 


- 28 


-105 


+ 19 


- 82 


+ 15 


+ 81 


+257 


+228 


+342 


+396 


+ 487 


+ 474 


1872 


- 93 


-164 


- 23 


— 101 


- 6 


- 76 


+ 96 


+ 76 


+ 167 


+230 


+393 


+393 


+ 536 


+ 475 


1873 


- 87 


-160 


-185 


- 96 


- 71 


- 72 


+ 84 


+ 78 


+152 


+226 


+417 


+ 393 


+512 


+479 


1874 


- 46 


-156 
-150 


- 90 


— IOI 

— IOO 


+ 40 


- 72 

- 66 


+ 141 


+ 78 
+ 81 


+ 158 


+ 222 
+218 


+384. 


+ 394 
+ 394 


+539 


+480 
+ 484 


1875 


- 71 




-160 




- 62 




+ 135 




+301 




+360 




+ 468 




1876 


- 87 


-146 


-148 


-103 


-136 


- 66 


+ 51 


+ 84 


+ 214 


+ 222 


+ 390 


+ 392 


+508 


+483 


1877 


-136 


-144 


- 70 


- 106 


-112 


- 69 


- 18 


+ 82 


+ 121 


+ 222 


+393 


+ 392 


+ 443 


+ 484 


1878 


-124 


-143 


- 14 


-104 


- 53 


- 7i 


+ 105 


+ 78 


+257 


+218 


+ 405 


+ 392 


+542 


+482 


1879 


-341 


-142 

-151 


-224 


- IOO 

-105 


-140 


- 7° 

- 73 


- 30 


+ 79 

+ 74 


+130 


+219 
+216 


+336 


+ 392 
+ 39° 


+397 


+ 485 
+481 


1880 


-161 




- 9 




- 25 




+ 81 




+217 




+ 387 




+ 456 




1881 


-428 


-iSi 


-213 


-IOI 


-152 


- 7i 


+ 6 


+ 75 


+260 


+216 


+ 327 


+ 390 


+ 456 


+ 480 


1882 


- 22 


— 162 


+ 8 


-106 


+ 31 


- 74 


+ 33 


+ 72 


+239 


+217 


+345 


+ 387 


+ 474 


+479 


1883 


-115 


-157 


- 48 


-IOI 


-186 


- 7° 


+ 78 


+ 7i 


+ 180 


+218 


+345 


+ 386 


+431 


+ 479 


1884 


- 53 


-*55 

-152 


- 81 


- IOO 

- 99 


- 31 


- 74 

- 73 


+ 39 


+ 7i 
+ 7° 


+205 


+ 217 
+216 


+366 


+ 384 
+ 384 


+ 474 


+477 
+477 


1885 


-189 




- 98 




-102 




+ 57 




+ 99 




+348 




+480 




1886 


-245 


-153 


-210 


- 99 


-146 


- 74 


+ 33 


+ 69 


+ 155 


+213 


+327 


+ 383 


+ 446 


+477 


1887 


-140 


-156 

- 155 


64 


— 102 

- IOI 


-105 


- 76 

- 77 


+ 9 


+ 68 
+ 66 


+214 


+211 
+ 211 


+468 


+ 381 
+ 384 


+536 


+ 476 
+478 



MEAN SCOTTISH METEOROLOGY. 



223 



Table XXIV. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 



Useful Plant-Growth Temperature in each Month being the Excess of Mean Temperature above 
42° -0 F. x into Number of Days in each Month (to even degrees only). 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Mean Month's 
























of Observed 


Successive 
Means of the 


Year 






















Quantities in 


repeated. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


each Year. 


Accumulating 
Years. 




+ 468 




+267 




+ 211 




- 69 




-127 




+ 113 




1856 


+558 


+ 513 


+ 423 


+ 345 


+236 


+ 224 


+ 51 


- 9 


+ 90 


- 18 


+185 


+ 149 


1857 


+493 


+ 506 


+375 


+ 355 


+ 90 


+ 179 


- 78 


- 32 


- 65 


- 34 


+142 


+ 147 


1858 


+490 


+ 502 


+ 309 


+ 344 


+118 


+ 164 


- 78 


- 44 


-248 


- 88 


+148 


+ 147 


1859 


+384 


+479 


+ 246 


+ 3 2 4 


+124 


+ 156 


- 87 


- 52 


-245 


-119 


+ 77 


+ 133 


1860 


+477 


+ 478 


+351 


+328 


+ 232 


+ 168 


-105 


- 61 


-124 


— 120 


+ 149 


+ 136 


1861 


+434 


+472 


+342 


+ 33° 


+ 158 


+ 167 


-147 


- 73 


- 6 


-104 


+127 


+ 134 


1862 


+ 425 


+ 466 


+243 


+ 320 


+ 149 


+ 165 


+ 33 


- 60 


- 37 


- 95 


+149 


+ 136 


1863 


+384 


+457 


+312 


+ 3i9 


+ 118 


+ 160 


- 33 


- 57 


- 81 


- 94 


+ 109 


+ 133 


1864 


+ 437 


+455 


+ 480 


+335 


+124 


+ 156 


- 18 


- 53 


+ 28 


- 82 


+152 


+ 135 


1865 


+403 


+45° 


+282 


+ 33° 


+205 


+ 160 


- 24 


- 5° 


- 43 


- 78 


+ 133 


+ 135 


1866 


+ 477 


+452 


+342 


+ 33 1 


+ 136 


+ 158 


- 12 


- 47 


- 99 


- 80 


+ 114 


+ 133 


1867 


+512 


+457 


+336 


+33* 


+ 87 


+ 153 


- 84 


- 5° 


- 43 


- 77 


+172 


+ 136 


1868 


+437 


+456 


+351 


+333 


+ 164 


+ 154 


- 48 


- 50 


-220 


- 87 


+134 


+ 136 


1869 


+496 


+458 


+348 


+ 334 


+133 


+ 152 


- 87 


- 52 


-264 


- 99 


+ 128 


+ 135 


1870 


+524 


+462 


+306 


+ 33 2 


+161 


+ 153 


-102 


- 56 


-124 


-100 


+134 


+ 135 


1871 


+ 450 


+462 


+285 


+ 329 


+118 


+ 151 


- 21 


- S3 


-115 


— IOI 


+149 


+ 136 


.1872 


+446 


+461 


+282 


+ 327 


+ 71 


+ 146 


- 24 


- 52 


+ 16 


- 95 


+134 


+ 136 


1873 


+431 


+ 459 


+ 324 


+327 


+ 140 


+ 146 


- 27 


- 5i 


-344 


-108 


+138 


+ 136 


1874 


+499 


+461 


+372 


+ 329 


+155 


+ 146 


- 84 


- 52 


- 96 


-107 


+151 


+ 137 


1875 


+490 


+463 


+294 


+ 327 


+242 


+ 151 


- 39 


- 52 


- 62 


-105 


+ 143 


+ 137 


1876 


+406 


+ 460 


+255 


+324 


+146 


+ 151 


+ 15 


- 49 


- 84 


— 104 


+113 


+ 136 


1877 


+515 


+ 462 


+369 


+326 


+214 


+ !54 


-120 


- 52 


-350 


-"5 


+146 


+ 137 


1878 


+434 


+ 461 


+285 


+ 324 


+124 


+ 152 


- 45 


- 5i 


-226 


— 120 


+ 58 


+ 133 


1879 


+539 


+464 


+ 396 


+327 


+ 12 


+ 147 


-105 


- 54 


-167 


— 121 


+135 


+ 133 


1880 


+356 


+ 460 


+312 


+ 326 


+ 87 


+ 144 


+ 90 


- 48 


-115 


— 121 


+ 82 


+ 131 


1881 


+ 474 


+ 461 


+294 


+325 


+186 


+ 146 


- 87 


- 49 


-260 


-126 


+143 


+ 132 


1882 


+440 


+ 460 


+324 


+ 325 


+136 


+ 146 


- 48 


- 49 


- 81 


-125 


+121 


+ 131 


1883 


+508 


+ 462 


+366 


+ 327 


+152 


+ 146 


- 54 


- 5° 


-164 


— 126 


+ 144 


+ 132 


1884 


+360 


+ 458 


+264 


+324 


+ 12 


+ 141 


- 51 


- 5° 


-118 


— 126 


+ 88 


+ 13° 


1885 


+440 


+458 


+ 306 


+324 


+232 


+ 144 


+ 24 


- 47 


-279 


-131 


+ 90 


+ 129 


1886 


+446 


+457 


+285 


+ 323 


+ 65 


+ 142 


- 72 


- 48 


-183 


-133 


+ 122 


+ 129 


1887 



224 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXV.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 



Progressive Accumulations of each kind of Useful Plant-Growth Temperature, both above and 
below 42°, from the beginning to the end of the year continuously. 



Year. 


January. 


February. 


March. 


April. 


May. 


June. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 

Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 
Mn. 


Ob. 


Su. 

Mn. 


1856 


-239 




- 




-309 




- 




-390 




- 




-390 




4- 69 




-390 




4-215 




-390 




+554 




1857 


-195 




- 




-271 




_ 




-358 




_ 




-358 




4- 21 




-358 




4-263 




-358 




+725 




1858 


- 84 


-217 


_ 


- 


-258 


-290 


_ 


™ 


-336 


-374 




- 


-336 


-374 


4- 54 


+ 45 


-336 


"374 


4-286 


+ 239 


-336 


-374 


+793 


+ 640 


1S59 


- 74 


-1/3 
-148 


- 


- 


-116 


-279 
-238 


- 




-116 


-361 
-300 


4-31 


4-8 


-119 


-361 
-301 


4- 31 


+ 48 
+44 


-119 


-361 
-301 


4-338 


+ 255 
+ 276 


-119 


-361 
-301 


+776 


+ 691 
+ 712 


1860 


-202 








-434 




- 




-546 




_ 




-561 




_ 




-561 




4-254 




-561 




+584 




1861 


-177 


-159 




~ 


-247 


-278 


_ 


- 


-275 


-349 


_ 


4-6 


-275 


-353 


4-102 


+ 35 


-275 


-353 


4-322 


+ 271 


-275 


-353 


+778 


+ 686 


1862 


-112 


-162 


_ 


- 


-165 


-272 


_ 


_ 


-295 


-337 


_ 


+ 5 


-295 


-34° 


4- 78 


4-46 


-295 


-34° 


4-360 


+ 280 


-295 


-34° 


+672 


+ 702 


1863 


-108 


-155 




— 


-130 


-257 


_ 


— 


-130 


-33 1 


4-28 


4-4 


-130 


-333 


4-100 


+ Si 


-130 


-333 


4-305 


+ 291 


-130 


-333 


+ 665 


+ 697 


1864 


-180 


-149 

-i5 2 


- 


- 


-426 


-241 
-262 


- 


- 


-566 


-306 
-335 


- 


+ 7 

+ 7 


-566 


-308 
"337 


4-123 


+ 57 
4-64 


-566 


-308 
-337 


+ 371 


+ 293 
+ 302 


-566 


-308 
-337 


+ 713 


+ 693 
+ 696 


1865 


-229 




_ 




-456 




_ 




-602 




_ 




-602 




4-135 




-602 




+ 411 




-602 




+ 864 




1866 


- 81 


-160 




- 


-229 


-281 




- 


-353 


-361 


_ 


4-6 


-353 


-363 


4- 60 


4-71 


-353 


-363 


+243 


+ 312 


-353 


-363 


+ 666 


+ 712 


1867 


-316 


-153 




- 


-333 


-276 


_ 


- 


-513 


-361 


_ 


+ 5 


-513 


-362 


4- 99 


4-70 


-513 


-362 


+269 


+ 306 


-513 


-362 


+ 638 


+ 708 


1868 


-140 


-166 




- 


-152 


-281 


_ 


- 


-152 


-373 


4-25 


+ 5 


-152 


-375 


4-145 


+ 73 


-152 


-375 


+ 436 


+ 3°3 


-152 


-375 


+ 844 


+ 702 


1869 


- 50 


— 164 

-156 


- 


- 


- 53 


-271 

-256 


- 


_ 


-183 


-356 
-344 


- 


4-6 
4-6 


-183 


-358 
-345 


4-147 


4-78 
+ 83 


-183 


-358 
-345 


+243 


+ 313 
+ 308 


-183 


-358 
-345 


+576 


+ 713 
+ 703 


1870 


-189 




.. 




-379 




- 




-457 




- 




-457 




4-147 




-457 




+ 411 




-457 




+819 




1871 


-254 


-158 




_ 


-282 


-264 


_ 


- 


-282 


-351 


4-19 


4-6 


-282 


-353 


4- 34 


+ 87 


-282 


-353 


+291 


+ 315 


-282 


-353 


+633 


+ 71 1 


1872 


- 93 


-164 


_ 


- 


-116 


-265 


_ 


- 


-122 


-347 


_ 


4-6 


-122 


-348 


4- 96 


4-84 


-122 


-348 


+263 


+ 314 


-122 


-348 


+656 


+ 706 


1873 


- 87 


- 160 




— 


-272 


-256 


_ 


- 


-343 


-334 


_ 


4-6 


-343 


-335 


4- 84 


+ 85 


-343 


-335 


+236 


+ 311 


-343 


-335 


+653 


+ 703 


1874 


- 46 


-156 

-150 


- 


- 


-136 


-257 
-251 


- 


- 


-136 


"334 
-324 


4-40 


4-6 
4-8 


-136 


-335 
-325 


4-181 


+ 85 
4-90 


-136 


-335 
-325 


+339 


+ 306 
+308 


-136 


-335 
-325 


+ 723 


+ 700 
+ 702 


1875 


- 71 




.. 




-231 




- 




-293 




- 




-293 




4-135 




-293 




+ 436 




-293 




+ 796 




1876 


- 87 


-146 




_ 


-235 


-250 


_ 


- 


-371 


-322 


_ 


+ 7 


-371 


-323 


4- 51 


4-92 


-371 


-323 


+265 


+ 315 


-371 


-323 


+655 


+ 706 


1877 


-136 


-144 




- 


-206 


-249 


_ 


- 


-318 


-325 


_ 


+7 


-336 


-326 


_ 


4-90 


-336 


-326 


+121 


+ 312 


-336 


-326 


+ 514 


+ 704 


1878 


-124 


-143 




- 


-138 


-247 




- 


-191 


-324 


_ 


4-6 


-191 


-326 


4-105 


4-86 


-191 


-326 


+362 


+ 3°4 


-191 


-326 


+ 767 


+ 695 


1879 


-341 


- 142 
-151 


- 




-565 


-242 
-256 


- 


- 


-705 


-3 J 9 
-335 


- 


4-6 
+ 6 


-735 


-320 
-337 


- 


4-87 
+ 83 


-735 


-320 
-337 


+ 130 


+ 306 
+ 299 


-735 


-320 
-337 


+ 466 


+ 698 
+ 689 


1880 


-161 




_ 




-170 




_ 




-195 




_ 




-195 




4- 81 




-195 




+ 298 




-195 




+ 685 




1881 


-428 


-151 




_ 


-641 


-252 


_ 


- 


-793 


-329 




4-6 


-793 


-332 


4- 6 


+ 83 


-793 


-332 


+266 


+ 299 


-793 


-33 2 


+ 593 


+ 689 


1882 


- 22 


-162 




- 


- 22 


-267 


+ 8 


- 


- 22 


-347 


4-39 


4-6 


- 22 


-35° 


4- 72 


4-80 


- 22 


-350 


+ 311 


+297 


- 22 


-3SO 


+ 656 


+ 685 


1883 


-115 


-157 




- 


-163 


-258 







-349 


-335 




+7 


-349 


-337 


4- 78 


4-80 


-349 


-337 


+258 


+ 298 


-349 


-337 


+ 603 


+ 684 


1884 


- 53 


-155 
-152 


- 




-134 


-255 

-250 


- 







-165 


-335 
-33° 


- 


4-6 
4-6 


-165 


-338 
-332 


4- 39 


4-80 
4-78 


-165 


-338 
-332 


+244 


+ 297 
+ 295 


-165 


-338 
-332 


+ 610 


+ 681 
+ 679 


1885 


-189 




_ 




-287 




_ 




-389 




- 




-389 




4- 57 




-389 




+ 156 




-389 




+ 504 




1886 


-245 


-153 




- 


-455 


-252 







-601 


-332 




4-6 


-601 


-334 


4- 33 


+ 78 


-601 


-334 


+ 188 


+ 290 


-601 


-334 


+515 


+ 673 


I--7 


-140 


-156 
-155 


- 


- 


-204 


-258 

-257 


- 






-309 


-34° 
-339 


- 


4-6 
4-6 


-309 


-342 
-341 


4- 9 


4-76 
+ 74 


-309 


-342 
-341 


+223 


+ 287 
+ 285 


-309 


-342 
-341 


+ 691 


4-668 
+ 668 



MEAN" SCOTTISH METEOROLOGY. 



225 



Table XXV. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 



Progressive Accumulations op each kind of Useful Plant-Growth Temperature, both above and below 42°, from 

the beginning to the end of the year continuously. 



July. 


August. ' September. 


October. 


November. 


December. 


Year 
reptd. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Below 42°. 


Above 42°. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


01). 


Sue. 

Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 

Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


Ob. 


Sue. 
Mn. 


-39C 




+ 1000 




-39C 




+ 1468 




-39C 




+ 112,1 




-390 




+ 1946 




-459 




+ 1946 




- 586 




+ 1946 




1856 


-358 




+1221 




-355 




+ 1779 




-358 




+2202 




-358 




+ 2438 




-358 




+2489 




- 35S 




+2579 




1857 


-33<i 


-374 


+1227 


+ 111C 


-336 


-374 


+ 172C 


+ 162^ 


-336 


-374 


+2095 


+ 1968 


-336 


"374 


+2185 


+ 2192 


-414 


-408 


+2185 


+2218 


- 479 


-472 


+2185 


+ 2262 


1858 


-119 


-361 
-301 


+1303 


+ 1149 
+ 1188 


-119 


-361 
-301 


+ 1793 


+ 1656 
+ 1690 


-119 


-361 
-301 


+2102 


+ 201 1 
+ 2034 


-119 


-361 
-301 


+2220 


+ 2190 
+ 2197 


-197 


-410 
-357 


+2220 


+ 2207 
+ 2210 


- 445 


-474 
-467 


+2220 


+ 2237 
+ 2232 


1859 


-561 




+1058 




-561 




+ 1442 




-561 




+ 1688 




-561 




+1812 




-648 




+1812 




- 893 




+ 1812 




1860 


-275 


-353 


+ 1237 


+ 1162 


-275 


-353 


+ 1714 


+ 1640 


-275 


-353 


+2065 


+ 1964 


-275 


-353 


+2297 


+ 2120 


-380 


-415 


+2297 


+ 2130 


- 504 


-552 


+2297 


+ 2148 


1861 


-295 


-34° 


+1038 


+ 1174 


-295 


-34° 


+1472 


+ 1653 


-295 


-34° 


+1814 


+ 1981 


-295 


-340 


+ 1972 


+ 2150 


-442 


-409 


+1972 


+ 2158 


- 448 


-S44 


+1972 


4-2173 


1862 


-130 


-333 


+1102 


+ «S5 


-130 


"333 


+1527 


+ 1627 


-130 


-333 


+ 1770 


+ 1957 


-130 


-333 


+ 1919 


+ 2124 


-130 


-414 


+1952 


+ 2132 


- 167 


-53° 


+1952 


+ 2144 


1863 


-566 


-308 

-337 


+ 1169 


+ 1148 
+ 1151 


-566 


-308 
-337 


+ 1553 


+ 1614 
+ 1608 


-566 


-308 
-337 


+ 1865 


+ 1934 
+ 1926 


-566 


-308 
-337 


+1983 


+ 2099 
+ 2086 


-599 


-378 
-4°3 


+1983 


+ 2109 
+ 2095 


- 680 


-485 
-5°7 


+1983 


+ 2120 
4-2105 


1864 


-602 




+1372 




-602 




+1809 




-602 




+ 2289 




-602 




+2413 




-620 




+2413 




- 620 




+2441 




1865 


-353 


-363 


+ 1128 


+ 1173 


-353 


-363 


+1531 


+ 1628 


-353 


-3 6 3 


+ 1813 


+ 1962 


-353 


-363 


+2018 


+ 2118 


-377 


-425 


+2018 


+ 2127 


- 420 


-518 


+2018 


4-2139 


1866 


-513 


-362 


+1035 


+ 1169 


-513 


-362 


+1512 


+ 1619 


-513 


-362 


+ 1854 


+ 1949 


-513 


-362 


+ 1990 


+ 2109 


-525 


-420 


+ 1990 


+ 2117 


- 624 


-509 


+ 1990 


+ 2128 


1867 


-152 


-375 


+ 1414 


+ 1158 


-152 


-375 


+ 1926 


+ 1610 


-152 


-375 


+ 2262 


+ 1941 


-152 


-375 


+2349 


+ 2099 


-236 


-429 


+2349 


+ 2106 


- 279 


-519 


+2349 


+ 2116 


1868 


-183 


-358 
-345 


+1112 


+ 1177 
+ 1173 


-183 


-358 
-345 


+1549 


+ 1634 
+ 1628 


-183 


-358 
-345 


+ 1900 


+ 1966 
+ 1961 


-183 


-358 
-345 


+2064 


+ 2119 
4-2IIS 


-231 


-414 
-401 


+2064 


4-2125 
+ 2121 


- 451 


-500 
-497 


+2064 


+ 2134 
+ 2129 


1869 


-457 




+ 1365 




-457 




+ 1861 




-457 




+2209 




-457 




+2342 




-544 




+ 2342 




- 808 




+2342 




1870 


-282 


-353 


+1120 


+ 1185 


-282 


-353 


+1644 


+ 1644 


-282 


-353 


+ 1950 


+ 1978 


-282 


-353 


+2111 


+ 2130 


-384 


-411 


+2111 


+ 2135 


- 508 


-517 


+2111 


+ 2143 


1871 


-122 


-348 


+1192 


+ 1181 


-122 


-348 


+ 1642 


+ 1644 


-122 


-348 


+1927 


+ 1976 


-122 


-348 


+2045 


+ 2129 


-143 


-409 


+2045 


+ 2134 


- 258 


-517 


+2045 


+ 2141 


1872 


-343 


-335 


+ 1165 


+ 1182 


-343 


-335 


+ 1611 


+ 1644 


-343 


-335 


+ 1893 


+ 1973 


-343 


-335 


+ 1964 


+ 2124 


-367 


-393 


+1964 


+ 2129 


- 367 


-502 


+ 1980 


+ 2136 


1873 


-136 


-335 
-325 


+1262 


+ 1181 

+ 1185 


-136 


-335 
-325 


+ 1693 


+ 1642 
+ 1645 


-136 


-335 
-325 


+2017 


+ 1968 
+ 1971 


-136 


-335 
-325 


+2157 


+2115 
+ 2117 


-163 


-392 
-380 


+2157 


+ 2120 
+ 2122 


- 507 


-494 
-495 


+2157 


+ 2127 
+ 2129 


1874 


-293 




+1264 




-293 




+1763 




-293 




+2135 




-293 




+ 2290 




-377 




+2290 




- 473 




+2290 




1875 


-371 


-323 


+ 1163 


+ 1189 


-371 


-323 


+1653 


+ 1650 


-371 


-323 


+1947 


+ 1979 


-371 


-323 


+2189 


+ 2126 


-410 


-380 


+2189 


+ 2130 


- 472 


-494 


+2189 


4-2137 


1876 


-336 


-326 


+ 957 


+ 1188 


-336 


-326 


+ 1363 


+ 1651 


-336 


-326 


+ 1618 


+ 1978 


-336 


-326 


+ 1764 


+ 2129 


-336 


-381 


+1779 


+2133 


- 420 


-493 


+1779 


4-2139 


1877 


-191 


-326 


+1309 


+ 1177 


-191 


-326 


+ 1824 


+ 1638 


-191 


-326 


+2193 


+ 1961 


-191 


-326 


+2407 


+ 2112 


-311 


-379 


+2407 


+ 2117 


- 661 


-489 


+ 2407 


+ 2123 


1878 


-735 


-320 
-337 


+ 863 


+ 1183 

+ 1170 


-735 


-320 
-337 


+1297 


+ 1646 
+ 163 1 


-735 


-320 

-337 


+1582 


+ 1971 
+ 1955 


-735 


-320 
-337 


+ 1706 


+2125 
+ 2108 


-780 


-376 
-393 


+ 1706 


+ 2129 
+ 2112 


-1006 


-497 
-518 


+1706 


+ 2135 
+ 2117 


1879 


-195 




+1141 




-195 




+ 1680 




-195 




+ 2076 




-195 




+2088 




-300 




+ 2088 




- 467 




+ 2088 




1880 


-793 


-332 


+1049 


+ 1169 


-793 


-332 


+ 1405 


+ 1633 


-793 


-332 


+1717 


+ 1960 


-793 


-33 2 


+ 1804 


+ 2107 


-793 


-389 


+1894 


+ 2111 


- 908 


-Si6 


+ 1894 


+ 2116 


18S1 


- 22 


-35° 


+1130 


+ 1164 


- 22 


-35° 


+ 1604 


+ 1624 


- 22 


-35° 


+ 1898 


+ I95I 


- 22 


-35° 


+ 2084 


+2095 


-109 


-4°S 


+ 2084 


+ 2102 


- 369 


-531 


+2084 


+ 2108 


1882 


-349 


-337 


+1034 


+ 1163 


-349 


-337 


+1474 


+ 1624 


-349 


-337 


+ 1798 


+ 1949 


-349 


-337 


+1934 


+2095 


-397 


-394 


+ 1934 


+ 2102 


- 478 


-525 


+ 1934 


+ 2107 


1883 


- 165 


-338 
-332 


+1084 


+ 1158 
+ 1156 


-165 


-338 
-33 2 


+ 1592 


+ 1618 
+ 1617 


-165 


-338 
-332 


+ 1958 


+ 1943 
+ 1944 


-165 


-338 
-332 


+2110 


+ 2089 
+ 2090 


-219 


-394 
-388 


+2110 


+ 2096 
+ 2096 


- 383 


-523 
-519 


+2110 


+ 2100 
+ 2101 


1884 


-389 




+ 984 




-389 




+ 1344 




-389 




+ 1608 




-389 




+ 1620 




-440 




+ 1620 




- 558 




+ 1620 




1885 


-601 


-334 


+ 961 


+ 1150 


-601 


-334 


+ 1401 


+ 1608 


-601 


-334 


+1707 


+ 1933 


-601 


-334 


+1939 


+ 2074 


-601 


-390 


+1963 


+ 2080 


- 880 


-520 


+1963 


+ 2085 


1886 


-309 


-342 
-341 


+1227 


+ 1144 
+ 1146 


-309 


-342 
-341 


+ 1673 


+ 1601 
+ 1604 


-309 


-342 
-341 


+ 1958 


+ 1925 
+ 1926 


-309 


-342 
-341 


+2023 


+ 2070 
+ 2068 


-381 


-396 
-396 


+ 2023 


+ 2077 
4-2075 


- 564 


-532 
-533 


+ 2023 


+ 2081 
+ 2079 


1887 



VOL. XXXV. PART 3. 



2 M 



226 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVI.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 



Final Accumulations, made good on the whole, of Useful Plant-Growth Temperature for each 
Month from the beginning to the end of the Year continuously. 





January. 


February. 


March. 


April. 


May. 


June. 


Year. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


1856 


-239 




-309 




-390 




-321 




-175 




+ 164 




1857 


-195 




-271 




-358 




-337 




- 95 




+367 




1858 


- 84 


-217 


-258 


-290 


-336 


-374 


-282 


-329 


- 50 


-135 


+ 457 


+ 266 


1859 


- 74 


-173 
-148 


-116 


-279 
-238 


- 85 


-361 
-292 


- 88 


-313 

-257 


+219 


- 107 
- 25 


+657 


+ 329 
+ 4 11 


1860 


-202 




-434 




-546 




-561 




-307 




+ 23 




1861 


-177 


-159 


-247 


-278 


-275 


-343 


-173 


-318 


+ 47 


- 82 


+503 


+ 334 


1862 


-112 


- 162 


-165 


-272 


-295 


-332 


-217 


-294 


+ 65 


- 60 


+ 377 


+ 362 


1863 


-108 


-155 


-130 


-2S7 


-102 


-326 


- 30 


-283 


+ 175 


- 42 


+ 535 


+ 364 


1864 


-180 


-149 
-152 


-426 


-241 
-262 


-566 


-298 
-328 


-443 


-251 
-272 


-195 


- 15 

- 35 


+ 147 


+ 385 
+359 


1865 


-229 




-456 




-602 




-467 




-191 




+262 




1866 


- 81 


- 160 


-229 


-281 


-353 


-356 


-293 


-292 


-110 


- 5i 


+313 


+ 349 


1867 


-316 


-IS3 


-333 


-276 


-513 


-355 


-414 


-292 


-244 


- 56 


+ 125 


+ 346 


1868 


-140 


-166 


-152 


-281 


-127 


-368 


- 7 


-302 


+284 


- 72 


+692 


+ 328 


1869 


- 50 


-164 
-156 


- 53 


— 271 
-256 


-183 


-350 
-338 


- 36 


-279 
-262 


+ 60 


- 44 

- 37 


+393 


+ 356 
+ 358 


1870 


-189 




-379 




-457 




-310 




- 46 




+362 




1871 


-254 


-158 


-282- 


-264 


-263 


-346 


-248 


-265 


+ 9 


- 38 


+351 


+ 358 


1872 


- 93 


-164 


-116 


-265 


-122 


-341 


- 26 


-264 


+ 141 


- 35 


+534 


+ 358 


1873 


- 87 


-160 


-272 


-256 


-343 


-328 


-259 


-250 


-107 


- 24 


+310 


+ 368 


1874 


- 46 


-IS6 
-150 


-136 


-257 
-251 


- 96 


-329 
-316 


+ 45 


-251 
-23S 


+203 


- 29 

- 17 


. +587 


+ 36S 
+ 377 


1875 


- 71 




-231 




-293 




-158 




+ 143 




+ 503 




1876 


- 87 


- 146 


-235 


-250 


-371 


-315 


-320 


-231 


-106 


- 9 


+284 


+ 383 


1877 


-136 


-144 


-206 


-249 


-318 


-3'8 


-336 


-235 


-215 


- 13 


+ 178 


+ 378 


1878 


-124 


-143 


-138 


-247 


-191 


-318 


- 86 


-240 


+ 171 


- 22 


+576 


+ 369 


1879 


-341 


-142 
-ISI 


-565 


-242 
-256 


-705 


-312 
-329 


-735 


-233 
-254 


-605 


- 14 

- 39 


-269 


+ 378 
+ 35i 


1880 


-161 




-170 




-195 




-114 




+ 103 




+ 490 




1881 


-428 


-151 


-641 


-252 


-793 


-3 2 3 


-787 


-249 


-527 


- 33 


-200 


+ 357 


1882 


- 22 


-162 


- 14 


-267 


+ 17 


-341 


+ 50 


-269 


+289 


- 52 


+634 


+ 335 


1883 


-115 


-iS7 


-163 


-258 


-349 


-328 


-271 


-258 


- 91 


- 39 


+254 


+ 346 


1884 


- 53 


-I5S 

-152 


-134 


-255 
-250 


-165 


-329 
-3 2 3 


-126 


-258 
-253 


+ 79 


- 4i 

- 37 


+445 


+ 343 
+ 347 


1885 


-189 




-287 




-389 




-332 




-233 




+115 




1886 


-245 


-153 


-455 


-252 


-601 


-325 


-568 


-256 


-413 


- 44 


- 86 


+ 339 


1887 


-140 


-156 
-i5S 


-204 


-258 
-256 


-309 


-334 
-334 


-300 


-266 
-267 


- 86 


- 56 

- 57 


+382 


+ 325 
+ 327 



MEAN SCOTTISH METEOROLOGY. 



227 



Table XXVI. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 



Final Accumulations, made good on the whole, of Useful Plant-Growth Temperature for each 
Month from the beginning to the end of the Year continuously. 



July. 


August. 


September. 


October. 


November. 


December. ' 


Year 
repeated. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 

Means. 


+ 610 






+ 1078 




+ 1345 




+ 1556 




+ 1487 




+ 1360 




1856 


+ 863 






+ 1421 




+ 1844 




+ 2080 




+ 2131 




+ 2221 




1857 




+ 


73 6 




+ 1250 




+ 1594 




+ 1818 




+ 1809 




+ 1790 




+ 891 






+ 1384 




+ 1759 




+ 1849 




+1771 




+ 1706 




1858 




+ 


788 




+ 1294 




+ 1649 




+ 1828 




+ I79 6 




+ 1762 




+1184 






+ 1674 




+1983 




+2101 




+2023 




+ 1775 




1859 




+ 


887 




+ 1389 




+ 1733 




+ 1896 




+ 1853 




+ 1766 




+ 497 






+ 881 




+1127 




+ 1251 




+ 1164 




+ 919 




1860 




+ 


809 




+ 1288 




+ 1612 




+ 1767 




+ 1715 




+ 1596 




+ 962 






+ 1439 




+ 1790 




+ 2022 




+1917 




+ 1793 




1861 




+ 


834 




+ I3 J 3 




+ 1641 




+ 1810 




+ 1749 




+ 1629 




+ 743 






+ 1177 




+ 1519 




+1677 




+ 1530 




+ 1524 




1862 




+ 


821 




+ 1293 




+ 1624 




+ 1791 




+ 1718 




+ 1614 




+ 972 






+ 1397 




+ 1640 




+ 1789 




+1822 




+1785 




1863 




+ 


840 




+ 1306 




+ 1626 




+ 1791 




+ 1731 




+ I635 




+ 603 






+ 987 




+1299 




+1417 




+ 1384 




+ 1303 




1864 




+ 


814 




+ 1271 




+ 1590 




+ 1749 




+ 1692 




+ 1598 




+ 770 






+ 1207 




+1687 




+ 1811 




+1793 




+ 1821 




1865 




+ 


810 




+ 1264 




+ 1599 




+ 1755 




+ 1702 




+ 1621 




+ 775 






+ 1178 




+ 1460 




+ 1665 




+ 1641 




+1598 




1866 




+ 


806 




+ 1257 




+ IS87 




+ 1747 




+ 1697 




+ 1619 




+ 522 






+ 999 




+ 1341 




+ 1477 




+ 1465 




+1366 




1867 




+ 


783 




+ 1235 




+ 1566 




+ 1725 




+ 1677 




+ 1598 




+ 1262 






+1774 




+2110 




+ 2197 




+2113 




+ 2070 




1868 




+ 


820 




+ 1277 




+ 1608 




+ 1761 




+ 1711 




+ 1634 




+ 929 






+ 1366 




+ 1717 




+1881 




+ 1833 




+1613 




1869 




+ 


827 




+ 1283 




+ 1616 




+ 1770 




+ 1720 




+ 1632 




+ 908 






+ 1404 




+1752 




+ 1885 




+ 1798 




+ 1534 




1870 




+ 


833 




+ 1291 




+ 1625 




+ 1777 




+ 1725 




+ 1626 




+ 838 






+ 1362 




+ 1668 




+ 1829 




+1727 




+ 1603 




1871 




+ 


833 




+ 1296 




+ 1628 




+ 1780 




+ 1725 




+ 1624 




+1070 






+ 1520 




+1805 




+ 1923 




+ 1902 




+1787 




1872 




+ 


847 




+ 1309 




+ 1638 




+ 1789 




+ I73S 




+ 1634 




+ 822 






+ 1268 




+ 1550 




+ 1621 




+ 1597 




+ 1613 




1873 




+ 


846 




+ 1306 




+ 1633 




+ 1780 




+ 1728 




+ 1633 




+ 1126 






+ 1557 




+ 1881 




+2021 




+ 1994 




+ 1650 




1874 




+ 


860 




+ 1320 




+ 1646 




+ 1792 




+ 1742 




+ 1634 




+ 971 






+ 1470 




+ 1842 




+ 1997 




+1913 




+ 1817 




1875 




+ 


866 




+ 1327 




+ 1656 




+ 1802 




+ 1750 




+ 1643 




+ 792 






+ 1282 




+ 1576 




+ 1818 




+1779 




+1717 




1876 




+ 


862 




+ 132S 




+ 1652 




+ 1803 




+ 1752 




+ 1646 




+ 621 






+ 1027 




+1282 




+ 1428 




+1443 




+1359 




1877 




+ 


851 




+ 1311 




+ 1635 




+ 1786 




+ 1738 




+ 1633 




+ 1118 






+ 1633 




+ 2002 




+2216 




+ 2096 




+ 1746 




1878 




+ 


863 




+ I3 2 S 




+ 1651 




+ 1805 




+ 1753 




+ 1638 




+ 128 






+ 562 




+ 847 




+ 971 




+ 926 




+ 700 




1879 




+ 


832 




+ 1294 




+ 1618 




+ 1770 




+ 1719 




+ 1599 




+ 946 






+1485 




+ 1881 




+ 1893 




+ 1788 




+ 1621 




1880 




+ 


837 




+ 1301 




+ 1628 




+ 1775 




+ 1721 




+ 1600 




+ 256 






+ 612 




+ 924 




+ 1011 




+ 1101 




+ 986 




1881 




+ 


815 




+ 1275 




+ 1601 




+ 1746 




+ 1698 




+ 1576 




+ 1108 






+ 1582 




+ 1876 




+ 2062 




+1975 




+ 1715 




1882 




+ 


825 




+ 1286 




+ 1611 




+ 1757 




+ 1708 




+ 1582 




+ 685 






+ 1125 




+1449 




+ 1585 




+ 1537 




+ 1456 




1883 




+ 


820 




+ 1280 




+ 1606 




+ I7SI 




+ 1702 




+ 1S77 




+ 919 






+ 1427 




+ 1793 




+ 1945 




+ 1891 




+1727 




1884 




+ 


824 




+ 1285 




+ 1612 




+ 1758 




+ 1708 




+ 1582 




+ 595 






+ 955 




+ 1219 




+ 1231 




+ 1180 




+ 1062 




1885 




+ 


816 




+ 1274 




+ J S99 




+ 1740 




+ 1690 




+ 156S 




+ 360 






+ 800 




+ 1106 




+ 1338 




+ 1362 




+ 1083 




1886 




+ 


801 




+ 1259 




+ IS83 




+ 1727 




+ 1680 




+ 1549 




+ 918 






+ 1364 




+ 1649 




+1714 




+ 1642 




+1459 




1887 




+ 


805 




+ 1262 




+ 158S 




+ 1727 




+ 1679 




+ 1546 





228 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TARLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1857. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Culloden . . . . . 


73-0 


15-1 


93-7 


26-1 


111-8 


24-5 


114-5 


27-1 


122-6 


30-0 


131-8 


31-1 


Castle Newe 










- 


- 


- 


- 


105-5 


14-0 


101-6 


21-0 


115-0 


29-0 


124-0 


28-0 


Braernar . 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Barry 










- 


- 


- 


- 


- 


- 


- 


19-0 


104-0 


24-0 


120-0 


31-0 


Kettins . 










- 


- 




- 


- 


- 


— 


- 


- 


— 


- 


- 


Perth . 










78-0 


12-0 


95-0 


17-0 


105-0 


20-0 


95-0 


22-0 


106-0 


26-0 


128-0 


34-0 


Pittenweem 










_ 


_ 


_ 


_ 


66-0 


- 


78-0 


- 


85-0 


- 


106-0 


_ 


Nookton . 










- 


_ 


72-0 


18-0 


72-0 


13-0 


88-0 


20-0 


103-0 


25-0 


118-0 


32-0 


Millfield . 










86-0 


10-0 


90-0 


23 


81-0 


18-0 


92-0 


20-0 


108-0 


25-0 


126-0 


35-0 


Row 










_ 


_ 


_ 


_ 


_ 


_ 


91-0 


26-4 


96-0 


29-0 


115-8 


36-8 


Moile House 










_ 


_ 


_ 


_ 


80-7 


29-5 


84-0 


29-7 


105-0 


34 


121-5 


36 


Smeaton 










- 


_ 


- 


_ 


- 


_ 


100-0 


22-0 


112-5 


28-5 


130-0 


29-0 


Tkirlestane Castle 








- 


- 


- 


- 


- 


- 


87-0 


21-0 


98-0 


28-0 


138-0 


30-0 




237 


37-1 


350-7 


84-1 


622-0 


119 


931-1 


228-2 


1155-1 


278-5 


1359-1 


322-9 




-=-3 


-=-3 


+ 4 


+4 


+7 


+ 6 


+10 


-=-10 


4-11 


-=-10 


+ 11 


-=-10 


Means 


79'° 


I2'4 


877 


21 'o 


88-9 


19-8 


93"i 


22-8 


105-0 


27-8 


123-6 


32'3 





January. 


February. 


March. 


April. 


May. 


June. 


1858. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Culloden 


61-0 


25-0 


82-5 


15-2 


87-0 


18-8 


1212 


22-2 


119-6 


32-4 


138-0 


41-2 


Castle Newe 












82-0 


19-0 


110-0 


2-0 


110-0 


16-0 


107-0 


18-0 


80-0 


27-0 


128-0 


36-0 


Braernar 












53-9 


15 


60-1 


6-5 


75-8 


13-1 


90-2 


16-2 


85-1 


25-8 


96-0 


30-2 


Banchory 












- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 


Barry 












63-5 


12-5 


76-0 


9-0 


104-5 


11-0 


110-0 


12-0 


115-0 


23 


140-0 


36-0 


Kettins . 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


_ 


Perth . 












81-0 


19-0 


88-0 


12-0 


102-0 


11-0 


112-0 


20-0 


109-0 


23 


130-0 


35-0 


Nookton 












53-0 


13-0 


65-0 


10-0 


86-0 


12-0 


101-0 


14-0 


109-0 


19-0 


118-0 


25-0 


Millfield . 












75-0 


11-0 


95-0 


10-0 


82-0 


7-0 


103-0 


10-0 


93-0 


20-0 


101-0 


30 


Otter House 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


_ 


_ 


Moile House 












52-0 


28-0 


63-0 


19-0 


97-5 


20-5 


- 


21-0 


- 


31-0 


- 


38-0 


Auchengray 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


1180 


33-0 


Paisley . 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Smeaton 












79-0 


18-0 


91-0 


13-0 


106-0 


17-0 


113-0 


17-0 


115-0 


26-0 


122-0 


33-0 


Thurston 












- 


- 


- 


- 


- 


- 


- 


- 


105-0 


_ 


108-0 


_ 


Thirlestane Castle 










77-0 


13-0 


87-0 


8-0 


117-0 


6 


124-0 


14 


117-0 


25-0 


130-0 


33-0 




677-4 


173-5 


817-6 


104-7 


967-8 


132-4 


981-4 


164-4 


1047-7 


252-2 


1329-0 


370-4 




-=-10 


+ 10 


-=-10 


+ 10 


+10 


+ 10 


-=-9 


-=-10 


+ 10 


-=-10 


+ 11 


+ 11 


Means 


677 


17 "4 


8i-8 


10-5 


96-8 


13-2 


109-0 


16 -4 


104-8 


25-2 


I20 - 8 


33 '7 



1859. 




January. 


February. 


March. 


April. 


May. 


June. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Culloden 


52-7 


21-7 


62-7 


22-1 


70-0 


20-1 


80-3 


23-0 


101-0 


27-9 


103-8 


36-8 


Castle Newe . 




74-0 


17 


75-0 


13-0 


74-0 


18-0 


85-0 


18-0 


103-0 


25-0 


106-0 


32-0 


Braernar .... 




63-0 


15-2 


62-1 


110 


66-2 


18-8 


74-2 


19-0 


98-2 


23-5 


113-0 


29-1 


Banchory 




- 


- 


78-0 


17-0 


78-0 


18-5 


910 


10-5 


93-5 


18-0 


93-5 


24 


Barry .... 




96-0 


18-0 


73-0 


13-0 


87-0 


17-0 


102-0 


16-0 


1250 


31-0 


131-0 


33-5 


Kettins .... 




- 


- 


- 


- 


_ 


- 


- 


17-0 


- 


- 


136-0 


30-0 


Perth .... 




85-0 


17-0 


94-0 


11-0 


101-0 


17-0 


115-0 


18-0 


130-0 


23-0 


135-0 


33-0 


Nookton .... 




64-0 


15-0 


76 


15-0 


85-0 


18-0 


98-0 


15-0 


_ 


20-0 


1150 


26-0 


Millfield. 




67-0 


14-0 


93-0 


7-0 


97-0 


14-0 


96-0 


13-0 


112-0 


20-0 


117-0 


25-0 


Otter House or Moile House 




64-0 


19-0 


_ 






_ 


90-2 


26-5 








42-0 


Paisley .... 




- 


- 


- 


23-0 


74-3 


19-5 


89-0 


17-0 


108-2 


23 


115-0 


28-5 


Smeaton. 




73-0 


13-0 


83-0 


14-0 


92-0 


13 


110-0 


16-0 


115-0 


17 


112-0 


22-0 


Thurston 




640 


_ 


74-0 


_ 


_ 


_ 


82-0 


_ 


_ 








Thirlestane Castle . 




89-0 


16-0 


89-0 


15-0 


107-0 


15-0 


102-0 


13-0 


128-0 


20-0 


- 


30 




791-7 


165-9 


859-8 


161-1 


931-5 


188-9' 


1214-7 


222-0 


1113-9 


248-4 


1277-3 


3919 




+ 11 


+10 


+ 11 


+ 11 


+ 11 


+ 11 


+ 13 


+ 13 


+ 10 


+ 11 


+ 11 


+ 13 


Means 


72*0 


16-6 


78-2 


14-6 


847 


17-2 


93 '4 


17T 


111-4 


22 - 6 


ii6 - i 


30-1 



MEAN SCOTTISH METEOROLOGY. 



229 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII. , XXVIII. 



1857. 



Culloden 

Caatle Newe 

Braemar 

Barry 

Kettins . 

Perth . 

Pittenweem 

Nookton . 

MMfield . 

Row 

Moile House 

Smeaton. 

Thirlestane Castle 



Means 



July. 



Max. 



124-7 
106-0 

116-0 
108-0 
104-0 
98-0 
121-0 
117-0 
105-8 
101-0 
128-0 
123-0 



1352-5 
-=-12 

II2'7 



Mill. 



37 9 
32 
19-5 
35-0 
33-0 
310 

33-0 
30 4 
40-2 
410 
39-0 
35-0 



407-0 
■4-12 

33"9 



August. 



Max. 



115-8 
122-0 

116-0 
129-0 
113-0 
94-0 
113-0 
115-0 

114-0 
125-0 
138-0 



1294-8 
Ml 

1 17 7 



Min. 



37-0 
32-0 
21-2 
35-0 
34-0 
38-0 

32-0 
34-0 

42-0 
39-0 
35 



3792 
-=-11 

34 '5 



September. 



Max. 



89-3 
103-0 

90-0 
105-0 
108-0 
112-0 

86-0 
100-0 
121-0 
108-0 

85-0 
123-0 
130-0 



1360-3 
-M3 

104-6 



Min. 



35-5 
360 
20-3 
35-0 
34-0 
31-0 

30 
30-0 
40-0 
39-0 
350 
30-0 



395-8 
■7-12 

33 "o 



October. 



Max. 



82-8 

113-0 

90-0 



99-0 

83-0 

109-0 

95-8 

77-0 

100-0 



849-6 



94 '4 



Min. 



28-0 
27-0 
10-0 



23-0 

22-0 
22-0 
33-7 
30-0 
28-0 



223-7 
H-9 

24 "9 



November. 



Max. 



72-8 
94-0 
90-0 
80-0 

83-0 
58-0 

88-0 

59-0 

85-0 

103-0 



812-8 
-M0 

81-3 



Min. 



25-8 

18-0 

4-0 

18-5 

20-0 

14-0 
19-0 

28-0 
20-0 
15-0 



182-3 

M0 

18-2 



December. 



Max. 



58-8 
81-0 
79-0 
65-0 

86-0 
59-0 
59-0 
70-0 



84-0 
89-0 



730-8 
-M0 

73"i 



Min. 



29-7 

27-0 

9-0 

17-0 

21-0 

20-0 
23-0 

33-5 
25-0 
190 



224-2 
-M0 

22 -4 





July. 


August. 


September. 


October. 


November. 


December. 


1858. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Culloden 


103-8 


40-4 


100-6 


40-1 


88-0 


32-2 


76-6 


27-2 


65-8 


12-7 


54-3 


24-8 


Castle Newe 










102-0 


38-0 


112-0 


33-0 


102-0 


30-0 


102-0 


25-0 


68-0 


7-0 


66-0 


20-0 


Braemar 










93 


31-2 


90-8 


29-8 


85-1 


26-5 


75-4 


20-5 


62-9 


7-5 


52-1 


22-0 


Banchory 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


57-0 


- 


Barry 










137-0 


37-0 


140-0 


33 


132-0 


32-0 


109-0 


23 


99-0 


16-0 


100-0 


12-0 


Kettins . 










135 


36 


124-0 


35-0 


126-0 


30-0 


- 


- 


- 


- 


- 


- 


Perth . 










1190 


35 


1250 


34 


123 


29-0 


107-0 


21-0 


97-0 


11-0 


85-0 


17-0 


Nookton 










119-0 


30-0 


117-0 


27-0 


106-0 


26-0 


- 


17-0 


74-0 


11-0 


59-0 


11-0 


Millfield . 










97-0 


23-0 


116-0 


26-0 


116-0 


26-0 


97-0 


19-0 


84-0 


14-0 


80-0 


15-0 


Otter House 










_ 


_ 


1190 


39-0 


110-0 


35-0 


96 


25-0 


81-0 


21-0 


60-0 


28-0 


Moile House 










_ 


35 


_ 


31-0 


- 


25-0 


- 


- 


_ 


- 


- 


- 


Auchengray 










_ 


- 


_ 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Paisley . 










- 


- 


106-2 


35-0 


104-5 


27-8 


86-0 


24-0 


- 


13-0 


53-0 


25-0 


Smeaton . 










1190 


31-0 


1180 


31-0 


1110 


28-0 


92 


18-0 


74-5 


9-0 


- 


14-0 


Thurston 










100-0 


_ 


107-0 


- 


110-0 


- 


81-0 


- 


75-0 


- 


63-0 


- 


Thirlestane Castle 








130-0 


32 


135-0 


32-0 


127-0 


27-0 


117-0 


22-0 


102-0 


10-0 


97-0 


16-0 




1254-8 


368-6 


1510-6 


425-9 


1440-6 


374-5 


1039-0 


241-7 


883-2 


132-2 


826-4 


204-8 




-Ml 


Ml 


-M3 


-M3 


-M3 


-M3 


-Ml 


Ml 


Ml 


-Ml 


M2 


Ml 


Means 


114-1 


33 "5 


Il6'2 


32-8 


1 10 8 


28-8 


94 "5 


22 "O 


80-3 


12 '0 


68-9 


18-6 





185£ 


. 






July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


1 Min. 


Max. 


Min. 


Max. 


Min. 


Culloden 


99-0 


41-4 


91-9 


38-4 


98-4 


31-9 


85-6 


21-7 


70-5 


24-1 


54-0 


11-2 


Castle Newe 










105-0 


36-0 


100-0 


35-0 


87-0 


29-5 


86-0 


18-0 


72-0 


23-0 


63-0 


0-2 


Braemar 










96-2 


29-0 


_ 


_ 


_ 


_ 


80-5 


10-9 


58-0 


19-0 


48-0 


-7-0 


Banchory 










100-0 


25-0 


110-0 


26-0 


94-0 


20-0 


100-0 


13-5 


79-0 


18-0 


62-0 


3-0 


Barry 










126-0 


35-0 


124-0 


34-0 


118-0 


27-0 


99-0 


9-0 


94-0 


15-0 


79-0 


10-0 


Kettins . 










_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


- 


- 


- 


Perth . 










_ 


_ 


134-0 


36 


130-0 


31-0 


112-0 


130 


92-0 


16-0 


81-0 


4-0 


Nookton 










115-0 


35-7 


110-0 


33-0 


97-6 


26-7 


95-6 


14-7 


64-6 


18-7 


48-6 


-6-0 


Millfield 










110-0 


30 


103 


32-0 


_ 


_ 


90-0 


10-0 


72-0 


17-0 


72-0 


5-0 


Moile House 










_ 


_ 




_ 


_ 


_ 


- 


_ 


- 


- 


- 


- 


Paisley . 










110-2 


31-0 


102-0 


32-0 


89-0 


26-0 


87-0 


11-5 


66 


16-5 


53-0 


3-0 


Smeaton 










124-0 


29-0 


111-0 


31-0 


103-0 


21-0 


111-0 


6-0 


81-0 


9-0 


67-0 


1-0 


Thurston 










_ 










_ 


_ 


_ 


_ 


- 


_ 


- 


Thirlestane Castle 








- 


30-0 


127-0 


32-0 


115-0 


27-0 


111-0 


7-0 


88-0 


13-0 


71-0 


6-0 




985-4 


322 1 


1112-9 


329-4 


932-0 


240-1 


1057-7 


135-3 


837-1 


189-3 


698-6 


30-4 




-f-9 


M0 


-M0 


-M0 


+ 9 


-=-9 


Ml 


-Ml 


-Ml 


-Ml 


-Ml 


Ml 


Means 


i°9 "5 


32-2 


111-3 


32 - 9 


103-6 


267 


96-2 


12-3 


76-1 


17-2 


63 "5 


2-8 



VOL. XXXV. PART 3. 



2n 



230 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1860. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


_ 


_ 


_ 


_ 


_ 


_ 


77-2 


29-0 


_ 


_ 


102 


41-4 


Kirkwall 








- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Harris 










- 


- 


- 


- 


- 


- 


- 


27-7 


- 


33-2 


- 


42-7 


S toni o way 










- 


- 


- 


- 


- 


- 


- 


25-0 


- 


33-0 


- 


- 


Culloden 










58 '0 


207 


64-6 


9 5 


70-8 


22-6 


83-9 


22-9 


91-4 


28-9 


87-1 


30-8 


Forres 










_ 


_ 


- 


- 


- 


- 


93-2 


25-4 


101-0 


307 


101-4 


34-8 


Castle Newe 










63-0 


10-0 


75-0 


-7-0 


75-0 


20-0 


93-0 


22-0 


103-0 


26-0 


89-0 


34-0 


Braemar 










_ 


- 


52-8 


-8-5 


- 


- 


- 


- 


- 


- 


86-0 


24-8 


Banchory 










71-5 


13-0 


86-0 


2-0 


81-0 


16-0 


88-0 


13-0 


95-0 


23 


92-0 


28-0 


Barry 










- 


- 


87-0 


8-2 


109-0 


18-7 


125-0 


20-9 


118-0 


31-7 


114-0 


36-0 


Kettins . 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Perth . 










85-0 


12-0 


103-0 


-4-0 


106-0 


20-0 


114-5 


20-0 


- 


- 


125-5 


32-0 


Nookton 










58-6 


9-7 


81-0 


7-0 


79-6 


20-7 


92-6 


14-7 


1076 


26-7 


117-0 


27-4 


Millfield . 










63-0 


11-0 


79-0 


3-5 


76-0 


17-0 


- 


- 


- 


- 


- 


- 


Callton Mor 










- 


21-5 


- 


16-0 


- 


23-0 


- 


25-0 


- 


29-0 


- 


35-0 


Oban 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Paisley . 










546 


15-0 


69-0 


-1-5 


71-7 


18-4 


91-7 


18-4 


108-0 


19-4 


89-7 


33-9 


Smeaton . 










70-0 


11-0 


83-0 


1-0 


87-0 


9-0 


98-0 


8-0 


114-0 


17-0 


108-0 


22-0 


Thurston 










72-0 


- 


89-0 


17-0 


86-0 


21 


105-0 


25-0 


118-0 


- 


119-0 


35-0 


Thirlestane Castle 








84-0 


2-0 


98-0 


o-o 


109-0 


10-0 


120-0 


15-0 


- 


24-0 


- 


25-0 




6797 


1-25-9 


967-4 


43-2 


951-1 


216-4 


1182-1 


312-0 


956-0 


322-6 


1230-7 


482-8 




-=-10 


■M0 


-fl2 


■i-13 


-Ml 


■fl2 


-M2 


-fl5 


+ 9 


■fl2 


■M2 


-M5 


Means 


68-o 


I2'6 


8o-6 


3'3 


86- 5 


i8-o 


98-5 


20'8 


I06'2 


26 '9 


102 "6 


32-2 





1861 








January. 


February. 


March. 


April. 


May. 


June. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


61-6 


„ 


_ 


_ 


_ 


._ 


_ 


_ 


_ 


_ 


_ 


_ 


Kirkwall 










51-5 


18-0 


60-6 


22-0 


67-0 


20-0 


87-6 


27-5 


89-1 


28-0 


- 


- 


Harris . 










64-6 


23-7 


77-4 


26-0 


67-2 


29-7 


82-2 


29-2 


77-4 


31-2 


114-9 


42-7 


Stornoway 










- 


- 


- 


- 


90-0 


25-5 


87-0 


22-0 


89-0 


24-0 


97-0 


32-0 


Culloden 










63-7 


13-1 


64-7 


211 


74-0 


26-8 


86-0 


22-6 


107-5 


23-6 


113-1 


36-7 


Portree . 










- 


_ 


67-6 


14-0 


74-0 


24-3 


102-0 


19-0 


113-0 


18-0 


118-2 


34-0 


Forres . 










60-7 


12-0 


70-6 


18-1 


81-6 


25-5 


97-8 


20-9 


107-0 


20-1 


118-5 


28-8 


Castle Newe 










68-0 


-10-0 


72-0 


12-0 


72-0 


28-0 


95-0 


25-0 


90-0 


25 


106-0 


37-0 


Braemar 










58-7 


- 2-2 


57-3 


11-0 


65-2 


23-0 


89-2 


13-0 


84-9 


13-5 


95-5 


340 


Banchory 










80-0 


8-0 


78-0 


7-0 


86-0 


18-0 


89-0 


19-0 


9S-0 


19-0 


99-0 


35-0 


Barry 










68-0 


12-5 


75-0 


12-0 


89-0 


25-0 


1100 


28-0 


107-0 


21-2 


118-0 


377 


Kettins . 










- 


6-0 


- 


12-0 


- 


23 


- 


20-0 


- 


23-0 


- 


36-0 


Perth . 










77-0 


4-0 


97-0 


10-0 


110-0 


25-0 


124-0 


20-0 


128-0 


19-0 


135-0 


42 


Nookton 










60-0 


3-4 


65-0 


13-4 


78-0 


21-4 


112-0 


17-4 


107-0 


15-4 


114-0 


28-4 


Callton Mor 










72-0 


15-5 


72 


20-0 


74-5 


26-2 


83-5 


24-0 


84-0 


21-0 


93-5 


36-0 


Oban 










51-0 


9-0 


59-0 


14-0 


71-0 


24-0 


88-0 


22-0 


94-0 


19-0 


108-0 


40-0 


Paisley . 










54-7 


2-4 


64-7 


11-9 


73-7 


27-4 


92-7 


20-4 


93-7 


17-5 


99-7 


41-9 


Douglas Castl 


B 








- 


- 


- 


- 


86-2 


25-0 


108-0 


17-2 


107-0 


13-0 


110-5 


29-0 


Smeaton 










69-0 


- 


90-0 


19-0 


92-0 


22-0 


108-0 


20-0 


111-0 


19-0 


115 


37-0 


Thurston 










86-5 


11-5 


92 -Q 


20-0 


96-0 


25-5 


105-0 


24-0 


110-0 


25-5 


121-0 


39 


Thirlestane Castle 






68-0 


- 7-0 


101-0 


o-o 


85-0 


20-0 


112-0 


15-0 


112-0 


14-0 


134-0 


31-0 


Mungo's Walls 






- 


- 


65-5 


13-5 


73-8 


22-8 


94-4 


20-9 


116-0 


18-7 


121-6 


361 




1115-0 


119-9 


1329 4 


277-0 


1606-2 


508-1 


1953-4 


447-1 


2025-6 


428-7 


2132-5 


714-3 




-=-17 


-=-16 


-=-18 


-=-19 


-=-20 


-=-21 


-=-20 


+ 21 


-=-20 


H-21 


■7-19 


+ 20 


Means 


65-6 


7"S 


73 - 9 


14-6 


80-3 


24-2 


977 


21-3 


101-3 


20 '4 


II2 - 2 


357 



MEAN SCOTTISH METEOROLOGY. 



231 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1860. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


93-2 


40-8 


96-6 


_ 


85-1 


_ 


87-0 


_ 


63-0 


_ 


_ 


_ 


Kirkwall 














- 


102 


31-0 


81-0 


23-0 


76-0 


22-0 


51-6 


22-0 


46-0 


18 


Harris . 












- 


42-2 


- 


43 


- 


38-8 


- 


33-6 


94-4 


28-2 


78-0 


19-0 


Stomoway 












- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 


Culloden 












98-6 


39-8 


- 


- 


977 


33-8 


68-7 


25-2 


59-8 


16-6 


49-9 


6-2 


Forres . 












110-4 


38-1 


104-2 


36-0 


107-5 


35-1 


69-7 


29-5 


63-2 


187 


52-0 


7-5 


Castle Newe 












110-0 


37-0 


99-0 


32-0 


102-0 


31-0 


91-0 


27-0 


77-0 


19-0 


60-0 


-19-0 


Braemar 












105-8 


31-0 


91-0 


30-0 


94-0 


25-0 


73-8 


24-4 


52-8 


9-3 


48-4 


- 0-1 


Banchory 












94-0 


35-0 


94-0 


26-0 


105-0 


22-0 


88-0 


20-0 


76-0 


_ 


58-0 


- 9-0 


Barry 












112-0 


38-0 


125-0 


33-0 


115-0 


27-0 


100-0 


21-5 


79-0 


21-0 


72-0 


4-5 


Kettins . 












- 


37-0 


- 


34-0 


- 


26-0 


- 


20-0 


- 


13-0 


_ 


- 3-0 


Perth . 












138-5 


40-0 


135-0 


37-0 


127-0 


18-0 


120-0 


21-0 


93-0 


15-0 


74-0 


- 5-0 


Nookton . 












114-0 


36-4 


119-0 


32-4 


105-0 


21-4 


92-0 


17-4 


69-0 


14-4 


59-0 


- 8-6 


Millfield 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




_ 


Callton Mor 












- 


35-0 


97-0 


33-0 


- 


29 


- 


25-0 


80-0 


21-5 


90-0 


8-0 


Oban 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


48-0 


8-2 


Paisley . 












109-7 


35-4 


115-0 


34-4 


110-0 


24-2 


88-0 


20-0 


717 


13-4 


66-0 


-110 


Smeaton 












114-0 


27-0 


113-0 


26 


108-0 


17-0 


98-0 


13 


82-0 


9-0 


65-0 


_ 


Thurston 












122-0 


39-0 


128-0 


39-0 


120-0 


32-5 


1100 


25-0 


97-0 


23-0 


80-0 


8-5 


Thirlestane Castle 










- 


310 


- 


26-0 


- 


16-0 


105-0 


21-0 


95-0 


14-0 


75-0 


-16-0 




1322-2 


582-7 


1418-8 


492-8 


1357-3 


419-8 


1267-2 


365-6 


1204-5 


258-1 


1021-3 


+ 8-2 




4-12 


4-16 


-=-13 


4-15 


-=-13 


-=-16 


4-14 


-=-16 


4-16 


4-15 


4-16 


4- 1-6 


Means 


no -2 


36-4 


109-1 


32-8 


104-4 


26-2 


9° '5 


22-8 


75'3 


17-2 


63-8 


o'S 





July. 


August. 


September. 


October. 


November. 


December. 


1861. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


_ 


_ 


_ 


_ 


86-5 


37-8 


80-0 


331 


- 


- 


- 


- 


Kirkwall 










102-6 


41-0 


87-6 


37-0 


_ 


- 


- 


- 


- 


- 


- 


- 


Kallin . 










111-9 


41-2 


_ 


39-0 


_ 


35-2 


83-4 


33-8 


65-4 


29-0 


53-9 


30-2 


Stomoway 










96-0 


33-5 


92-0 


33-0 


99 


30-5 


77-0 


29-5 


70-0 


18-0 


67-0 


25-0 


Culloden 










96-0 


39-7 


88-8 


38-8 


103-9 


34-9 


76-7 


24-9 


62-8 


13-6 


58-9 


22-6 


Portree . 










116-5 


300 


93-9 


34-0 


91-8 


26-5 


81-3 


22-0 


687 


13-5 


68-5 


20-1 


Forres 










105-2 


36-0 


98-4 


36-6 


90-6 


32-3 


771 


21-7 


65-3 


21-7 


67-3 


16-8 


Castle Newe 










101-0 


38-0 


102-0 


36-0 


94-0 


25-0 


108-0 


23-0 


77-0 


10-0 


79-0 


15-0 


Braemar 










85-0 


34-0 


851 


32-0 


80-0 


30-8 


79-0 


24-0 


72-0 


13-5 


64-0 


14-0 


Banchory 










99-0 


32-0 


100-0 


30-0 


93 


23-0 


92-0 


20-0 


69-0 


5-0 


72-0 


15-0 


Barry 










121-0 


42-5 


117-0 


41-0 


116-0 


39-0 


101-0 


27-0 


79-0 


17-0 


65-0 


19-0 


Kettins . 










_ 


36-0 


_ 


38-0 


_ 


31-0 


- 


26-0 


- 


12-0 


- 


14-0 


Perth . 










123-0 


37-0 


112-0 


35-0 


126-0 


30-0 


115-0 


22-0 


97-0 


14-0 


73 


120 


Nookton 










111-0 


31-4 


103-0 


33-4 


112-0 


30-4 


87-0 


23-4 


65 


12-4 


58-0 


13-4 


Callton Mor 










87-5 


32-0 


82-0 


36-5 


_ 


_ 


80 -0 


27-0 


69-0 


16 


65-8 


22-0 


Oban 










107-0 


37-0 


96-0 


38-0 


87-0 


33-0 


72-0 


26 


51-0 


19-0 


51-0 


19-0 


Paisley . 










106-2 


39-5 


88-7 


39-4 


93-2 


28-4 


75-0 


24-4 


67-7 


16-4 


59-7 


16-4 


Douglas Castl 










104-5 


36-0 


96-0 


35-8 


102-2 


26-8 


- 


- 


76-0 


3-5 


68-0 


10-5 


Smeaton 










110-0 


38-0 


112-0 


36-0 


111-0 


27-0 


94-0 


24-0 


73-0 


14-0 


66-0 


12-0 


Thurston 










119-0 


41-0 


106-0 


43-0 


114-0 


30-0 


119-0 


30-5 


97-0 


16-0 


78-0 


18-5 


Thirlestane Castle 








117-0 


32 


107-0 


- 


111-0 


23-0 


109-0 


16 


92-0 


3-0 


86-0 


8-0 


Mungo's Walls 








- 


- 


- 


- 


- 


- 


- 


- 


_ 


— 


~ 






2019-4 


727-8 


1767-5 


692-5 


1711-2 


574-6 


1606-5 


478 3 


1316-9 


267-6 


1201-1 


323-5 




4-19 


-=-20 


-=-18 


4-19 


4-17 


4-19 


4-18 


4-19 


4-18 


4-19 


4-18 


4-19 


Means 


106-3 


3 6 '4 


98-2 


3 6 '4 


100-7 


30-2 


89-2 


25-2 


73 ' 2 


14-1 


667 


17-0 



232 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TARLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVIL, XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1862. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


51-4 


26 6 


77-0 


24-4 


89-0 


16-2 


82-0 


24-0 


89-0 


33 6 


_ 


_ 


Kirkwall 










- 


- 


57-5 


18-4 


71-1 


11-4 


85-1 


18-9 


87-9 


31-0 


97-3 


31-9 


Harris . 










59-4 


28-7 


77-4 


26-7 


74-5 


22-2 


88-4 


29-0 


100-7 


33-8 


91-4 


32-6 


Stornoway 










63-0 


26 


73-0 


22 


78-0 


14-0 


79-0 


23-0 


85-0 


26-0 


90-5 


31-0 


Culloden 










64-8 


24-1 


76-0 


15-5 


89-0 


9-7 


111-2 


22-6 


1121 


30-1 


107-8 


33-5 


Portree . 










70-5 


23 


86-5 


13-2 


97-7 


121 


98-7 


22-5 


114-7 


22-0 


115-2 


26-5 


Forres . 










72-0 


28-0 


74-8 


17-0 


78-5 


11-5 


106-2 


25-5 


102-4 


28-3 


105-0 


32-0 


Castle Newe 










74-0 


27-0 


89-0 


9-0 


89-0 


11-0 


76-0 


2J-0 


83-0 


25-0 


830 


28-0 


Braemar 










82-0 


25-0 


- 


11-9 


101-0 


11-3 


77-0 


22-0 


88-0 


25-2 


90-5 


31-2 


Banchory 










79-0 


19-0 


72-0 


14-0 


85-0 


6-0 


81-0 


20-0 


83-0 


22-0 


89-0 


28-0 


Barry 










69-0 


23-0 


94-0 


14-0 


1100 


8-0 


- 


24-0 


- 


- 


- 


- 


Kettins . 










- 


25-0 


_ 


14-0 


- 


8-0 


_ 


20-0 


- 


28-0 


- 


34-0 


Perth . 










_ 


22-0 


91-0 


14-0 


- 


_ 


114-0 


22-0 


118-0 


26-0 


129-0 


33-0 


Nookton 










65-0 


21-4 


710 


11-4 


87-0 


8-4 


98-0 


17-4 


107 -0 


23-4 


109-0 


29-4 


Balloch Castle 










- 


- 


- 


- 


75-0 


9-0 


99-0 


20-0 


108-0 


28 


1100 


36-0 


Otter House 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


90-0 


_ 


Callton Mor 










64 5 


25-0 


73-5 


160 


74-0 


11-5 


78-2 


18-0 


75-0 


24-0 


85-0 


32-9 


Oban 










- 


- 


62-0 


160 


71-0 


16-0 


90-0 


22-0 


94-0 


27-0 


99-0 


30-0 


Paisley . 










60-0 


24-0 


70-7 


11-9 


70-7 


15-4 


80-7 


11-9 


877 


25-4 


101-7 


32-4 


Douglas Castl 


e 








66-0 


17-0 


82-0 


9-8 


- 


- 


- 


_ 


91-0 


21-0 


110-0 


24-0 


Smeaton 










66-0 


23 


740 


17-0 


88-0 


3 


1050 


22-0 


107-0 


25 


105-0 


30-0 


Thurston 










80-0 


20-2 


810 


22-2 


92-0 


11-2 


108-0 


23-0 


105-0 


32-0 


110-0 


360 


Thirlestane Castle 








82-0 


13 


91-0 


8-0 


97-0 


4-0 


106-0 


17-0 


113-2 


18-3 


125 


25-0 




1168-6 


441-0 


1473-4 


326-4 


1617-5 


219-9 


1763-5 


445-8 


1951-7 


555-1 


2043-4 


617-4 




-=-17 


-=-19 


+ 19 


+21 


-=-19 


-=-20 


+ 19 


+ 21 


+20 


-=-21 


-=-20 


-=-20 


Means 


687 


23-2 


77 "5 


iS'S 


85-1 


n -o 


92-8 


21 '2 


97 -6 


26-4 


I02 "2 


30-9 





January. 


February. 


March. 


April. 


May. 


June. 


1863. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


59-0 


20-2 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


Sandwick 










557 


29-7 


61-7 


21-3 


68-2 


23-6 


77-2 


26-5 


910 


24-2 


113-2 


31-3 


Kirkwall 










53-6 


23-9 


58-1 


22-4 


70-8 


26-0 


82-2 


27-2 


92-4 


26-9 


98-7 


34-9 


Harris . 










64-9 


28-9 


69-4 


30-1 


72-4 


27-1 


83-5 


30-9 


88-5 


349 


104-5 


42-9 


Stornoway 










61-0 


23-0 


73-0 


24 


70-0 


25-0 


75-0 


25-0 


77-0 


28-0 


85-0 


28-0 


Culloden 










57-1 


17-6 


82-4 


23-7 


100-0 


19-7 


106-0 


27-7 


108-6 


31-6 


106-2 


37 6 


Portree 










- 


- 


73-0 


21-6 


90-4 


18-7 


99-8 


23-0 


96-8 


23-1 


103-6 


27-8 


Forres . 










59-0 


14-0 


79-5 


25-1 


79-2 


18-7 


- 


- 


- 


- 


- 


- 


Castle Newe 










69-0 


22-0 


75-0 


26-0 


77-0 


16-0 


78-0 


25-0 


85-0 


28-0 


90-0 


27 


Braemar 










60-0 


8-0 


78-0 


21-4 


66-2 


21-0 


74-5 


26-0 


99-0 


29 


99-0 


32 2 


Banchory 










64-0 


170 


78-0 


15 


84-0 


15-0 


81-0 


15-0 


88-0 


21-0 


91-0 


22-0 


Kettins 










_ 


23 


_ 


15 


- 


18-0 


- 


25-0 


- 


25-0 


- 


32-0 


Perth . 










- 


_ 


_ 


- 


114-0 


17-0 


- 


23-0 


- 


- 


118-0 


30 


Nookton 










53 


18-4 


75-0 


17-4 


85-0 


16-4 


93-0 


18-4 


101-0 


19-4 


105-0 


24-4 


Dollar . 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Balloch CastU 










52-0 


25-0 


58-0 


18-0 


75-0 


18-0 


94-0 


20-0 


110-0 


22-0 


103 


29-0 


Otter House 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Drishaig 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Callton Mor 










65-5 


26-0 


60-0 


26-0 


72-0 


20-5 


75-5 


24-0 


77-0 


26-0 


84-5 


32-0 


Oban 










49-0 


23 


51-0 


22-0 


68 


20-0 


82-0 


26-0 


99-0 


29-0 


104-0 


35-0 


Paisley . 










74-5 


27-4 


70 5 


18-4 


77-7 


19-4 


81-5 


25-4 


95-0 


25-4 


93-5 


35-4 


Douglas Cast 


e 








65-0 


20 


_ 


- 


83-0 


13-5 


95-0 


19-0 


93-0 


23 


106 


28-0 


Smeaton 










64-0 


18-0 


82-0 


15-0 


90-0 


16-0 


95 


210 


107-0 


24-0 


110-0 


27-0 


Thurston 










86 


25-0 


102-0 


26-0 


98-0 


22-0 


101-0 


29-0 


102-0 


30-5 


- 


36-5 


Thirlestane Castle 








780 


16-0 


93 


9-0 


99 


11-0 


102-0 


18-0 


112-0 


22-0 


1140 


25-0 


South Cairn . 








- 


- 


55-0 


32 


62-0 


29-0 


72 


32-0 


76-0 


32-0 


82-0 


410 




1190-3 


426-1 


1374-6 


429-4 


1701 -9 


431-6 


1648-2 


507-1 


17983 


525-0 


1911-2 


659-0 




+ 19 


+20 


+ 19 


-=-20 


-=-21 


+22 


+19 


+ 21 


+ 19 


+20 


+ 19 


+21 


Means 


627 


BI'3 


72 - 3 


21 - 5 


81 -o 


19-6 


867 


24-1 


94 -6 


26-2 


ico'6 


3''4 



MEAN SCOTTISH METEOROLOGY. 



233 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 



1862 




July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


_ 


_ 


99-4 


38-4 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


Kirkwall 




100-7 


36 


97-6 


31-9 


94-1 


27-6 


69-1 


27-4 


55-6 


18-9 


53-4 


28-8 


Harris, Kallin, and 


Benbecula 


89-6 


39-9 


110-2 


45-9 


101-2 


43-1 


82-6 


32-9 


70-4 


311 


71-4 


28-1 


Stornoway 




83-0 


36-0 


85-0 


38-0 


89-0 


31-0 


77-0 


27-0 


73-0 


22-0 


59-0 


27-0 


Culloden 




112-2 


39-6 


113-0 


36-8 


105-3 


34-7 


98-8 


27-7 


74-8 


16-9 


54-5 


22-6 


Portree . 




110-0 


35-6 


108-7 


32-0 


109-7 


26-0 


94-5 


18-4 


78-7 


16-1 


710 


26-0 


Forres 




100-8 


37-5 


105-0 


34-9 


99-1 


34-0 


91-0 


26-3 


71-0 


12-5 


58-0 


23-5 


Castle Newe . 




88-0 


30 


89-0 


30-0 


92-0 


29 


97-0 


24-0 


70-0 


12-0 


57-0 


27-0 


Braemar 




86-5 


34-0 


88-0 


31-0 


98-2 


29-0 


93-2 


26-2 


70-0 


11-2 


56-0 


26-0 


Banchory 




94-0 


30-0 


100-0 


31-0 


102-0 


27-0 


103-0 


20-0 


74-0 


10-0 


66-0 


19 


Barry 




- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




Kettins . 




- 


35-0 


- 


35-0 


- 


- 


- 


28-0 


- 


10-0 


- 


25-0 


Perth . 




118-0 


36-0 


132-0 


30-0 


138-0 


28-0 


124-0 


21-0 


_ 


_ 


_ 


_ 


Nookton 




106-0 


32-4 


108-0 


32-4 


104-0 


25-4 


92-0 


18-4 


69-0 


11-4 


54-0 


19-4 


Balloch Castle 




103-0 


370 


106-0 


40-0 


109-0 


32-0 


80-0 


25-0 


53-0 


14-0 


_ 


_ 


Otter House . 




90-7 


- 


_ 


_ 


95-5 


- 


92-0 


_ 


_ 


_ 


_ 


_ 


Callton Mor . 




79-0 


34-5 


88-0 


37-5 


110-0 


29-0 


80-0 


23-2 


70-5 


21-5 


55-5 


29-0 


Oban 




96 


33-0 


99-0 


37-0 


95-0 


29-0 


75-0 


25-0 


56-0 


17-0 


_ 


_ 


Paisley . 




88-7 


37-4 


103-5 


35-4 


108-7 


27-9 


89-0 


26-4 


74-5 


13-6 


64-3 


21-6 


Douglas Castle 




103-5 


22-5 


107-5 


24-0 


113-5 


19-5 


107-0 


20-5 


75-0 


9-0 


66-0 


15-0 


Smeaton 




111-0 


35-0 


113-0 


32-0 


109-0 


26-0 


94-0 


26-0 


82-0 


12-0 


68-0 


23-0 


Thurston 




114-0 


39-0 


120-0 


39-5 


127-0 


33-0 


112-0 


29-0 


98 


18-0 


60-0 


28-0 


Thirlestane Castle 




105-0 


25-0 


120-0 


26 


122-0 


18-0 


121-0 


13-0 


105-0 


8-0 


79-0 


22-0 




1979-7 


685-4 


2092-9 


718-7 


2122-3 


549-2 


1872-2 


485-4 


1320-5 


285-2 


993-1 


411-0 




-=-20 


+20 


-=-20 


+21 


+ 20 


+ 19 


+20 


+ 20 


+ 18 


+ 19 


+ 16 


+ 17 


Means 


99 -o 


34'3 


104-6 


34 '2 


io6'i 


28-9 


93 '6 


24'3 


73'4 


15 '0 


62-1 


24-2 





1863 










July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


East Yell 


_ 


_ 


_ 


_ 




_ 


_ 


_ 


_ 


_ 


_ 


_ 


Sand wick 












111-2 


34-0 


94-2 


32-7 


88-0 


31-8 


65 


23-7 


55-8 


23-2 


50-2 


- 


Kirkwall 












106-4 


31-3 


95-6 


30-4 


89-6 


31-4 


68-8 


25-4 


- 


22-9 


_ 


22-9 


Harris . 












104-3 


41-9 


103-5 


42 T 


97-0 


41-6 


- 


- 


- 


- 


- 


- 


Stornoway 












89-0 


290 


90-0 


32-0 


88-0 


30-0 


72-0 


28-0 


75-0 


26-0 


58-0 


20-0 


Culloden 












114-0 


33-4 


107-0 


35-6 


102-0 


34-6 


82-2 


25-1 


68-5 


21-9 


57-0 


18 T 


Portree 












117-4 


24-8 


114-8 


30-8 


105-1 


28-0 


92-0 


22-7 


73-4 


16-0 


57-0 


11-0 


Forres 












- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Castle Newe 












100-0 


28-0 


96-0 


31-0 


95-0 


27-0 


80-0 


21-0 


74-0 


20-0 


65-0 


13-0 


Braemar 












104-2 


310 


107-0 


31-8 


97-8 


32-3 


91-0 


21-0 


83-8 


15-0 


71-0 


14-0 


Banchory 












101-0 


22-0 


99-0 


27-0 


92-0 


20-0 


88-0 


18-0 


- 


- 


68-0 


9-0 


Kettins 












- 


28-0 


_ 


32-0 


- 


30-0 


_ 


22-0 


- 


17-0 


- 


20-0 


Perth . 












149-0 


25-0 


127-0 


29-0 


115-0 


25-0 


106-0 


18-0 


88-0 


14-0 


73-0 


8-0 


Nookton 












118-0 


16-4 


110-0 


25-4 


95-0 


22-4 


78-0 


13-4 


63-0 


12-4 


53-0 


12-4 


Dollar . 












- 


_ 


_ 


_ 


_ 


_ 


_ 


- 


73-7 


21-7 


64-7 


21-7 


Balloch Castle 












1110 


30-0 


108-0 


33 


95-0 


32-0 


69-0 


26-0 


56-0 


18-0 


- 


- 


Otter House 












130-0 


- 


126-0 


- 


110-0 


- 


83-0 


- 


- 


- 


- 


- 


Drishaig 












- 


- 


_ 


- 


- 


_ 


105-6 


20-0 


- 


- 


- 


- 


Callton Mor 












85-5 


29-0 


93-0 


31-2 


79-5 


32-0 


74-0 


26-0 


- 


- 


65-0 


21-5 


Oban 












102-0 


29-0 


98-0 


32-0 


87-0 


31-0 


65-0 


24-0 


54-0 


21-0 


50-0 


19-0 


Paisley . 












99-3 


26-9 


99-5 


32-4 


85 3 


31-2 


88-0 


211 


77-7 


21-0 


65-7 


16-4 


Douglas Casth 












- 


_ 


107-5 


25-0 


98-0 


25-0 


- 


- 


70-0 


13-0 


- 


- 


Smeaton 












110-0 


24-0 


108-0 


27-0 


98-0 


26-0 


87-0 


21-0 


70-0 


13-0 


67-0 


11-0 


Thurston 












110-0 


30-0 


106-0 


39-0 


101-0 


35-0 


96-0 


29-0 


76-0 


23-0 


60-0 


20-0 


Thirlestane Castle 










118-0 


20-0 


116-0 


24-0 


113-0 


26-0 


106-0 


18-0 


91-0 


12-0 


68-0 


11-0 


South Cairn . 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




2080-3 


533-7 


2106-1 


623-4 


1931-3 


592-3 


1596-6 


423-4 


1149-9 


331-1 


992-6 


269-0 




-=-19 


+ 19 


-=-20 


-^20 


+ 20 


-=-20 


-=-19 


+ 19 


^-16 


-=-18 


-=-16 


+ 17 


Means 


109-5 


28-1 


i°S - 3 


31-2 


966 


29-6 


84-0 


22-3 


71-9 


18-4 


62-0 


i5'8 



VOL. XXXV. PART 3. 



2 



234 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1864. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


.Min. 


Sand wick 


4S-1 


17-3 


62-0 


7-4 


74-3 


14-3 


93-2 


23-2 


1017 


24-7 


1010 


33-4 


Kirkwall 








_ 


20-4 


_ 


10-6 


717 


16-6 


86-8 


22-6 


94-4 


23-9 


104-2 


33-9 


Stornoway 








57-0 


26-0 


73-0 


23-0 


72-0 


22-0 


88-0 


26-0 


85-0 


29-0 


90-0 


34-0 


Culloilen 








66-1 


13-4 


73-5 


14-6 


87-5 


13-6 


106-0 


26-4 


106-8 


28-8 


108-3 


29-6 


Portree 








63-2 


17-2 


80-3 


11-5 


94-0 


15-8 


_ 


_ 


106-2 


25-8 


106-8 


24-8 


Castle Newe 








710 


7-0 


73-0 


-1-0 


75-0 


-2-0 


90-0 


24-0 


94-0 


22-0 


93-0 


26-0 


Braemar 








75-0 


8-8 


82-0 


3-3 


92-0 


3-0 


105-0 


25-7 


108-9 


. 26-8 


98-0 


26-8 


Banchory 








68-0 


6-0 


73-0 


-30 


- 


- 


95-0 


15-0 


95-0 


20-0 


93 


22-0 


Kettins . 








- 


8-0 


_ 


5-0 


- 


2-0 


- 


22-0 


- 


27-0 


- 


27-0 


Perth . 








73-0 


8-0 


80-0 


8-0 


87-0 


6-0 


110-0 


20-0 


115-0 


23-0 


116-0 


28-0 


Nookton . 








67-0 


6-4 


68-0 


7-4 


78-0 


12-4 


95-0 


19-4 


110-0 


20-4 


106 


22-4 


Dollar . 








in 


16-7 


83-0 


16-0 


88-7 


20-7 


101-7 


27-7 


101-7 


27-7 


99-7 


29-7 


Bloomhill or Cardross 






- 


_ 


_ 


_ 


- 


_ 


- 


28-0 


- 


29-5 


- 


31-5 


Balloch Castle 






50-0 


9 


53-0 


9-0 


78-0 


10-0 


102-0 


25-0 


111-0 


25-0 


110-0 


26-0 


Callton Mor . 






64-0 


17-5 


64-5 


17-5 


65-5 


19-9 


86-0 


26-5 


115-0 


26-0 


100-0 


27-0 


Oban 






_ 


_ 


50-0 


14-3 


71-0 


20-0 


94-0 


28-0 


101-0 


28-0 


109-0 


27-0 


Paisley . 






72-2 


5-4 


63-8 


5-4 


77-9 


8-9 


91-2 


27-7 


971 


25-4 


86-1 


23-9 


Glasgow 






73 


12-2 


72-0 


13-1 


86-8 


18-0 


- 


27-3 


- 


27-5 


- 


28-2 


Douglas Castle 






63-0 


14-0 


81-0 


7-0 


91-0 


8-0 


108-0 


25-0 


117-0 


18-0 


106-0 


26-0 


Smeaton 






69-0 


5-0 


70-0 


1-0 


92-0 


10-0 


98-0 


18-0 


1170 


15-0 


110-0 


16-0 


Thurston 






71-0 


15-0 


86-0 


12-0 


80-0 


23-0 


96-0 


30-0 


120-0 


29-0 


109-0 


32-0 


Thirlestane Castle . 






68-0 


3-0 


96-0 


2-0 


111-0 


o-o 


117-0 


18-0 


134-0 


190 


117-0 


22-0 


South Cairn 






- 


- 


- 


- 


51-0 


24-0 


77-0 


34-0 


93-0 


37-0 


90-0 


40-0 




1196-3 


236-3 


1384-1 


184-1 


1624-4 


266-2 


1839-9 


539-5 


2123-8 


578-5 


2053-1 


637-2 




■7-18 


•7-20 


-=-19 


-7-21 


-f-20 


-f-21 


■fl9 


-f-22 


-f-20 


-f-23 


-f-20 


-f-23 


Means 


66-5 


n-8 


72-8 


8-8 


8i-2 


12 "7 


96-8 


24 - S 


106 "2 


25-1 


102-7 


277 





January. 


February. 


March. 


April. 


May. 


June. 


1865. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Mill. 


Max. 


Min. 


Sanilwick ..... 


47-7 


8-2 


58-1 


21-0 


74-4 


25-3 


81-4 


21-2 


102-0 


25-2 


94-7 


27-4 


Kirkwall 










_ 


6-4 


48-2 


20-4 


67-2 


21-0 


90-0 


21-0 


98-8 


32-0 


87-8 


29-5 


Stornoway 










55-0 


13-0 


62 


15-0 


_ 


_ 


84-0 


26-0 


88-0 


25-0 


97-0 


29-0 


Culloden 










54-2 


11-6 


71-0 


11-2 


91-8 


23-5 


114-3 


26-4 


116-1 


81 '1 


126-4 


35-6 


Portree . 










67-8 


7-0 


77-8 


6-8 


92-3 


14-8 


109-3 


23-3 


121-0 


25-8 


121-0 


28-3 


Castle Newe 










65-0 


-7-0 


71-0 


3-0 


80-0 


15-0 


92-0 


21-0 


101-0 


26 


106-0 


27-0 


Braemar . 










68-0 


5-3 


85-0 


5-0 


840 


19-0 


112-8 


23-2 


110-8 


29-3 


121-0 


33-0 


Aberdeen 










- 


_ 


119-0 


11-8 


114-0 


23-9 


91-2 


23-0 


93 


28-0 


94-0 


30-2 


Banchory 










63 


1-0 


70-0 


-6-0 


79-0 


15-0 


100-0 


12-0 


98-0 


19-0 


101-0 


23-0 


Kettins . 










- 


6-0 


_ 


_ 


_ 


18-0 


- 


20-0 


- 


22-0 


- 


320 


Perth . 










71-0 


7-0 


82-0 


4 


87-0 


16-0 


119-0 


17-0 


142-0 


180 


1350 


30-0 


Nookton . 










60-0 


3-4 


71-0 


1-4 


79-0 


14-4 


104-0 


18-4 


1130 


23-4 


112-0 


28-4 


Dollar . 










71-7 


12-7 


_ 


_ 


78-7 


24-7 


95-7 


26-7 


104-7 


28-7 


107-7 


36-7 


Cardross 










_ 


18-0 


_ 


9 


_ 


16-5 


- 


26-0 




29-5 




38-0 


Balloch Castlt 










_ 


11-0 


50-0 


1-0 


71-0 


14 


98-0 


20-0 


109-0 


22-0 


123-0 


32-0 


Callton Mor 










51-0 


14-5 


55-5 


9-0 


68-0 


15-0 


95-5 


20-0 


112-0 


22-0 


106-8 


32-8 


Oban 










47-0 


16-0 


58-0 


9-0 


72-0 


20-0 


- 


- 


- 


- 


- 


- 


Paisley . 










69-5 


4-4 


88-5 


-3-0 


79-5 


16-4 


85-5 


20-6 


93-5 


32-2 


100-1 


38-6 


Glasgow 










71-1 


9-0 


88-4 


-0-3 


98-7 


19-1 


130-2 


25-1 


124-0 


28-8 


137-2 


36-7 


Douglas Castl 










65-0 


10-0 


76-0 


6-0 


83-0 


12-0 


111-0 


23-0 


114-0 


26-0 


118-0 


33-0 


Smeaton 










66-0 


-3-0 


83-0 


5-0 


86-0 


10-0 


115-0 


10-0 


118-0 


19-0 


123-0 


19-0 


Thurston 










64-0 


14-0 


71-0 


15-0 


82-0 


26-0 


102-0 


28-0 


108-0 


35 


115-0 


35-0 


Thirlestane Castle 








82-0 


o-o 


93-0 


-4-0 


101-0 


13-0 


131-0 


17-0 


124-0 


18-0 


132 


18-0 


South Cairn . 








52-0 


270 


57-0 


22-0 


74-0 


26-0 


83-0 


34-0 


102-0 


37-0 


97-0 


40-0 




1191-0 


195-5 


1535-5 


162-3 


1742-6 


418-6 


2144-9 


502-9 


2292-9 


603-0 


2355-7 


713-2 




-f-19 


-f-23 


-=-21 


-f-22 


-f-21 


-f-23 


-f-21 


-f-23 


-f-21 


-f-23 


-f-21 


-f-23 


Means 


627 


8-5 


73' 1 


7'4 


83-0 


18-2 


102- 1 


21-9 


109-2 


26-2 


1 12 - 2 


31-0 




MEAN SCOTTISH METEOROLOGY. 



235 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTEEMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





1864. 








July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick ..... 


105-2 


36-4 


96-4 


31-4 


91-4 


33 3 


80 8 


27-2 


59-0 


23-2 


52-0 


21-2 


Kirkwall 










102-8 


36-6 


96-6 


40-6 


88-9 


33-3 


_ 


24-4 


_ 


21-4 


_ 


22-9 


Stornoway 










86-0 


42-0 


88-0 


38-0 


83-0 


38-0 


86-0 


29-0 


67-0 


28-0 


52-0 


32-0 


Culloden 










119-4 


38-7 


104-0 


34-1 


105 


32-6 


99 -8 


27-4 


70-5 


21-7 


56-8 


19-6 


Portree . 










117-5 


37-0 


114-0 


25-2 


_ 


_ 


91-8 


22-8 


77-0 


20-0 


53-5 


19-0 


Castle Newe 










109-0 


34-0 


104-0 


28-0 


95-0 


27-0 


89-0 


21-0 


72-0 


19-0 


64-0 


14-0 


Braemar 










118-0 


36-0 


111-0 


33-0 


104-0 


31-0 


103-0 


25-0 


81-0 


19-2 


75-0 


14-5 


Banchory 










98-0 


21-0 


97-0 


21-0 


95-0 


20-0 


87-0 


13-0 


78-0 


10-0 


69-0 


15-0 


Kettins . 










- 


34-0 


- 


27-0 




29-0 


_ 


23-0 


_ 


18-0 


_ 


18-0 


Perth . 










130-0 


32-0 


118-0 


26-0 


112-0 


29-0 


120-0 


150 


85-0 


15-0 


69-0 


16-0 


Nookton 










107-0 


28-4 


104-0 


27-4 


98-0 


27-4 


88-0 


15-4 


77-0 


15-4 


55-0 


11-4 


Dollar . 










104-7 


36-7 


104-7 


33-7 


103-7 


34-7 


94-7 


24-7 


87-7 


21-7 


60-7 


22-7 


Bloomhill or Cardross 








- 


39-4 


_ 


35-0 


_ 


35-5 


_ 


_ 


_ 


25-0 


_ 


23-0 


Balloch Castle 








117-0 


35-0 


118-0 


_ 


95-0 


32-0 


80-0 


22-0 


_ 


20-0 


_ 


20-0 


Callton Mor . 








123-5 


37-5 


108-5 


28-0 


86-0 


29-0 


77-0 


18-0 


64-0 


17-0 


53-0 


13-0 


Oban 








111-0 


39-0 


100-0 


30-0 


90-0 


34-0 


76-0 


25-0 


59-0 


24-0 


53-0 


21-0 


Paisley . 








105-0 


35-4 


100-3 


28-9 


86-5 


33-4 


78-5 


22-2 


_ 


_ 


- 


- 


Glasgow 








130-7 


38-3 


121-8 


27-2 


114-0 


_ 


103-0 


_ 


66-2 


19-0 


65-1 


21-3 


Douglas Castle 








115-0 


34-0 


119-0 


_ 


104-0 


- 


91-0 


22-0 


_ 


_ 


60-0 


17-5 


Smeaton 








121-0 


27-0 


117-0 


20-0 


105-0 


22-0 


95-0 


14-0 


74-0 


12-0 


64-0 


15-0 


Thurston 








116-0 


39-0 


112-0 


35-0 


105-0 


37-0 


94-0 


28-0 


80-0 


26-0 


60-5 


24-0 


Thirlestane Castle . 








126-0 


34-0 


130-0 


21-0 


120-0 


22-0 


108-0 


17-0 


98-0 


15-0 


78-0 


12-0 


South Cairn . 








93-0 


40-0 


90-0 


38-0 


85-0 


40-0 


82-0 


36 


65-0 


27-0 


58-0 


26-0 




2355-8 


811-4 


2254-3 


628-5 


1966-5 


620-2 


1824-6 


472-1 


1260-4 


417-6 


1098-6 


419-1 




-=-21 


-f23 


-=-21 


*21 


-=-20 


-=-20 


-=-20 


-=r21 


-M7 


T-21 


-=-18 


-=-22 


Meams 


II2'2 


35 '3 


107-3 


29-9 


98-3 


31-0 


91 "2 


22-5 


74-1 


19-9 


61 - o 


19-0 





186£ 








July. 


August 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


109-2 


33 2 


97-2 


36-8 


97-0 


37-0 


81-6 


27-2 


63-2 


23-2 


55-2 


22-0 


Kirkwall 










101-8 


29-7 


90-0 


26-5 


87-6 


31-2 


73 6 


23-6 


- 


21-3 


- 


24-5 


Stornoway 










85-0 


25-0 


92-0 


24-0 


_ 


_ 


95-0 


9-0 


73-0 


- 


64-0 


26-0 


Culloden 










119-0 


35-1 


117-4 


40-5 


108-2 


32-6 


102-1 


22-6 


70-0 


22-1 


- 


- 


Portree . 










- 


_ 


118-2 


30-0 


107-3 


32-8 


107-2 


22-3 


77-3 


120 


62-0 


22-1 


Castle Newe 










105-0 


30-0 


97-0 


30-0 


108-0 


27-0 


107-0 


22-0 


76-0 


21-0 


70-0 


22-0 


Braemar . 










114-8 


31-0 


111-0 


31-3 


113-8 


28-0 


116-8 


19-0 


75-0 


11-3 


72-2 


25-2 


Aberdeen 










97-0 


33-0 


90-9 


29-0 


101-0 


29-0 


101-5 


17-0 


80-0 


19-5 


75-7 


23-3 


Banchory 










104-0 


27-0 


93-0 


21-0 


102-0 


_ 


102-0 


14-0 


76-0 


14-0 


73-0 


17-0 


Kettins . 










- 


33-0 


_ 


32-0 


_ 


33-0 


_ 


17-0 


- 


16 


- 


22-0 


Perth . 










125-0 


32-0 


114-0 


32 


114-0 


28-0 


109-0 


130 


92-0 


12-0 


75-0 


18-0 


Nookton 










119-0 


33-4 


108-0 


29-4 


107-0 


30-4 


93-0 


18-4 


73-0 


15-4 


58-0 


17-4 


Dollar . 










101-7 


37-7 


100-7 


35-7 


107-7 


35-7 


101-0 


23-0 


- 


- 


67-7 


23-7 


Cardross 










- 


40-0 


_ 


38-5 




37-0 


_ 


25-0 


_ 


24-0 


- 


23-0 


Balloch Castle 










116-0 


34-0 


105-0 


33-0 


102-0 


28-0 


84-0 


20-0 


57-0 


15-0 


52-0 


19-0 


Callton Mor 










112-8 


36-3 


109-5 


30-7 


_ 




81-0 


20-0 


60-4 


22-5 


53-7 


24-8 


Oban 










_ 


_ 








_ 


_ 


_ 


_ 


_ 


_ 


_ 


Paisley . 










99-8 


28-2 


98-3 


32-4 


98-5 


34-2 


85-9 


16-8 


78-5 


16-2 


68-7 


19-8 


Glasgow 










135-4 


36-7 


128-6 


34-6 


120-2 


35-2 


94-0 


22-0 


92-3 


22-6 


79-0 


19-3 


Douglas Casth 










119-0 


33-0 


113-0 


37-0 


112-0 


32-0 


111-0 


19-5 


81-0 


17-0 


73-0 


19-0 


Smeaton 










1 


24-0 


112-0 


22-0 


115-0 


_ 


105-0 


20-0 


78-0 


20-0 


74 


19-0 


Thurston 










112-0 


39-0 


110-0 


39-5 


111-0 


40-0 


108-0 


27-5 


96-0 


25-0 


81-0 


25-0 


Thirlestane Castle 








129-0 


22-0 


120-0 


23-0 


122-0 


23-0 


123-0 


14-0 


100-0 


9-0 


84-0 


110 


South Cairn . 








105-0 


43 


90-0 


40-0 


86-0 


42-0 


72-0 


29-0 


56-0 


29-0 


54-0 


32-0 




2231-5 


716-3 


2215-8 


728-9 


2020-3 


616-1 


20537 


461-9 


1454-7 


388-1 


1292-2 


475-1 




-f20 


-f22 


-1-21 


-=-23 


-=-19 


-=-19 


•7- 21 


-=-23 


-f-19 


-h21 


-=-19 


-=-22 


Means 


in-6 


32-6 


io5\5 


3i'7 


106-3 


32-4 


97-8 


20 "i 


76-6 


18-5 


68-o 


21'6 



'236 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1866. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Nandwick ..... 


52-0 


24-0 


66-2 


8-8 


71-2 


18-0 


94-7 


19-2 


997 


10-2 


113 


28-3 


Kirkwall 










- 


_ 


_ 


_ 


_ 


9-0 


76-6 


19-5 


95-5 


13-5 


102-1 


25-0 


Stornoway 










50-0 


12-0 


70-0 


11-0 


81-0 


9-0 


86-0 


8-0 


92-0 


_ 


94-0 


- 


( 'ullodell 










62-0 


17-6 


84-2 


12-8 


_ 


_ 


- 


- 


117-0 


22-6 


131-0 


31-6 


Portree . 
Elgin 
Castle Newe 










62-0 


9-0 


76-5 


12-5 


92-8 


15-0 


115-8 


15-8 


115-0 


21-9 


124-1 


28-0 










71-0 


12-0 


71-0 


5-0 


77-0 


-4-0 


97-0 


22-0 


91-0 


24-0 


109-0 


28-0 


Braemar 










72-3 


11-8 


88-3 


9-8 


90-2 


-2-0 


106-0 


21-2 


106-5 


25-8 


117-0 


30-0 


Aberdeen 










64-0 


130 


75-9 


13-0 


79-0 


9-0 


75-3 


21-0 


86-7 


19-3 


97-4 


24-0 


Banchory 










65-0 


4-0 


74-0 


4-0 


78-0 


3-0 


93-0 


15-0 


90-0 


14-0 


98-0 


23-0 


Kettins . 










_ 


11-0 


_ 


14-0 


_ 


9-0 


- 


18-0 


- 


22-0 


- 


26-0 


Perth . 










78-0 


9-0 


85-0 


13 


89-0 


12-0 


97-0 


15-0 


104-0 


20-0 


105-0 


30-0 


Nookton . 










56-0 


13-4 


69-0 


14-4 


80-0 


9-4 


99-0 


13-4 


106-0 


21-4 


117-0 


25-4 


Dollar . 










617 


19-7 


73-7 


19-7 


_ 


_ 


- 


- 


97-7 


24-7 


104-0 


30-7 


Cardross 










_ 


15-0 


_ 


17-0 


_ 


17-0 


- 


23-0 


_ 


24-0 


- 


35-0 


Balloch Castle 










52 -0 


5-0 


49-0 


10-0 


65-0 


10-0 


88-0 


19-0 


99-0 


22-0 


116-0 


27-0 


Cairndow 










74-6 


15-2 


99-6 


17-0 


106-9 


17-3 


122-5 


23-3 


127-8 


27-6 


141-6 


29-3 


Callton Mor 










535 


15-5 


60-3 


21-5 


74-2 


17-4 


97-5 


21-0 


105-4 


24-5 


123-5 


30-9 


Eallabus 










_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


- 


- 


- 


Paisley . 










58-8 


11-4 


79-0 


15-0 


74-0 


_ 


80-5 


20-4 


93-5 


20-4 


94-3 


24-0 


Glasgow . 










82 1 


12-3 


89-2 


10-6 


105-7 


16-2 


114-7 


20-1 


120-7 


23-1 


131-7 


26-5 


Douglas Castl 










62-0 


7-0 


76-0 


12-0 


80-0 


10-0 


85-0 


24-0 


102-0 


20-0 


111-0 


26-0 


Smeaton . 










77-0 


12-0 


79-0 


17-0 


86-0 


10-0 


101-0 


14-0 


116-0 


17-0 


130-0 


23-0 


Thurston 










64-0 


20-0 


84-0 


25-0 


77-0 


19-0 


92-0 


25-0 


106-0 


22-0 


116-0 


26-5 


Thirlestane Castle 








82-0 


9-0 


100-0 


15-0 


102-0 


o-o 


1180 


13-0 


118-0 


12-0 


135-0 


130 


South Cairn . 








54-0 


24-0 


54-0 


29-0 


- 


- 


70-0 


300 


75-0 


29-0 


84-0 


39-0 




1354-0 


302-9 


1603-9 


327-1 


1509-0 


204-3 


1909-6 


420-9 


2264-5 


481-0 


2494-7 


630-2 




4-21 


-=-23 


+ 21 


-=-23 


T-18 


4-20 


4-20 


-=-22 


4-22 


4-23 


4-22 


4-23 


Means 


64 - 5 


13-2 


76-4 


14-2 


83-8 


IO'2 


95 '5 


19-1 


102 -9 


20-9 


"3 '4 


27-4 





1867 








January. 


February. 


March. 


April. 


May. 


June. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


51-0 


6-5 


65-4 


17-8 


70-2 


6-0 


76-5 


23-0 


96-0 


21-5 


94-4 


32-5 


Kirkwall 










- 


3-6 


- 


17-6 


- 


8-2 


- 


19-5 


- 


- 


89-5 


33-0 


Stornoway 










49-0 


1-0 


71-0 


23-0 


73-0 


8-0 


76-0 


- 


84-0 


- 


88-0 


- 


Culloden 










57-2 


4-6 


76-0 


22 6 


_ 


_ 


100-0 


25-7 


113-0 


29-5 


134-0 


34-6 


Portree . 










61-3 


6-0 


86-7 


20-0 


93-5 


7-0 


101-0 


25-0 


115-7 


25-8 


119-3 


26 


Elgin . 










- 


4-0 


_ 


20-0 


_ 


10-5 


- 


_ 


- 




_ 


_ 


Castle Newe . 










63-0 


-9-0 


77-0 


17-0 


96-0 


2-0 


78-0 


25-0 


83-0 


25-0 


108 -C 


31-0 


Braemar 










79-2 


3-5 


77-8 


16-2 


88-0 


o-o 


78-0 


25-2 


86-0 


27-0 


106-0 


35-3 


Aberdeen 










74-3 


8-4 


81-6 


19-5 


93-0 


13-6 


84-2 


23-5 


92-0 


23-0 


94-5 


28-0 


Banchory 










69-0 


3-0 


83-0 


9 


80-0 


- 


85-0 


15-0 


86-0 


- 


98-0 


22-0 


Kettins . 










- 


4-0 


_ 


20-0 


_ 


12-0 


_ 


28-0 


_ 


28-0 


_ 


35-0 


Perth . 










74-0 


6-0 


85-0 


18-0 


_ 


_ 


91-0 


26-0 


98-0 


22-0 


116-0 


25-0 


Nookton 










58-0 


6-4 


72-0 


16-4 


83-0 


10-4 


99-0 


23-4 


108-0 


19-4 


116-0 


34-4 


Dollar . 










- 


- 


69-7 


20-7 


81-7 


16-7 


82-7 


26-7 


84-7 


31-7 


93-7 


387 


Cardross 










- 


13-0 


- 


22-0 


_ 


16-5 


- 


29-0 


- 


30-0 


- 


30-0 


Balloch Castle 










- 


- 


58-0 


15-0 


71-0 


9-0 


89-0 


25-0 


103-0 


- 


117-0 


34-0 


Cairndow 










79-1 


14-0 


101-1 


20-1 


105-8 


17-1 


106-3 


27-4 


123-4 


24-8 


124-1 


28-3 


Calton Mor 










- 


8-5 


_ 


20-0 


- 


15-0 


95-0 


27-0 


104-0 


26-0 


116-5 


30-0 


Eallabus . 










67-5 


- 


79-0 


- 


90-4 


_ 


95-2 


_ 


106-1 


_ 


111-6 


_ 


Paisley . 










59-5 


5-4 


68-5 


11-4 


72-0 


8-0 


75-5 


23-8 


79-5 


25-4 


94-7 


33-9 


Glasgow 










79-1 


6-0 


94-2 


15-6 


110-0 


15-3 


120-2 


26-6 


125-7 


25-0 


134-6 


33-7 


Douglas Castl 










59-0 


2-0 


81-0 


11-0 


_ 


- 


87-0 


26-0 


87-0 


22-0 


111-0 


31-0 


Smeaton . 










73-0 


9-0 


89-0 


17-0 


88-0 


12-0 


98-0 


26-0 


108-0 


21-0 


116-0 


30-0 


Thurston 










56-0 


120 


77-0 


23-5 


74-0 


21-0 


84-0 


31-5 


95-0 


28-0 


104-0 


38-0 


Thirlestane Castle 








82 


- 


95-0 


12-0 


100-0 


1-0 


102-0 


26-0 


124-0 


22-0 


135-0 


25-0 


South Cairn . 








- 


18-0 


- 


- 


54-0 


22-0 


- 


- 


105-0 


30-0 


110-0 


38-0 




11 HI -2 


135-9 


1588-0 


425-4 


1523-6 


231-3 


1903-6 


554-3 


2207-1 


507-1 


2531-9 


727-4 




4-18 


4-22 


4-20 


4-24 


4-18 


4-21 


4-21 


4-22 


4-22 


4-20 


4-23 


4-23 


Means 


66-2 


6-2 


79 '4 


177 


84-6 


II "O 


90-6 


25-2 


100-3 


25 "4 


IIO'I 


31-6 



MEAN SCOTTISH METEOROLOGY. 



237 



Table XXVIa. con tinned.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1866. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


940 


32 2 


94-2 


31-0 


96-2 


30-1 


78-4 


23-7 


58-8 


23-8 


51-0 


22-4 


Kirkwall 










92 4 


31-6 


87-6 


30-4 


80-1 


27-0 


71-6 


21-5 


- 


21-9 


_ 


23-6 


Stornoway 










96-0 


- 


87-0 


- 


87-0 


- 


89-0 


26-0 


69-0 


18-0 


52-0 


20-0 


Culloden 










119-9 


38-6 


115-8 


38-8 


101-2 


31-1 


95-0 


25-4 


S3-0 


22-8 


57-5 


24-6 


Portree . 










- 


- 


118-0 


32-0 


107-1 


29 3 


102-5 


25-2 


77-0 


16-3 


_ 


_ 


Elgin 










- 


- 


- 


33-5 


- 


- 


- 


24-5 


- 


25-0 


_ 


23-5 


Castle Newe 










104-0 


31-0 


96-0 


28-0 


87-0 


28-0 


100-0 


23-0 


70-5 


22-0 


64-0 


19-0 


Braemar . 










121-0 


35-0 


120-2 


32-4 


105-8 


28-0 


125-0 


16-2 


92-0 


17-0 


73-3 


20-4 


Aberdeen 










105-0 


27-9 


93-5 


28-0 


96-5 


23-5 


98-8 


26-2 


83-0 


- 


70-0 


18-4 


Banchory 








. 


111-0 


31-0 


95-0 


28-0 


91-0 


22-0 


99-0 


19-0 


78-0 


13-0 


63-0 


10-0 


Kettins . 










_ 


33-0 


- 


32-0 


- 


28-0 


- 


25-0 


- 


20-0 


_ 


21-0 


Perth . 










121-0 


33 


- 


- 


110-0 


26-0 


- 


- 


78-0 


16-0 


69-0 


18-0 


Kookton . 










114-0 


34-4 


108-0 


33-4 


106-0 


25-4 


93-0 


23-4 


66-0 


14-4 


55-0 


13-4 


Dollar . 










107-7 


33-7 


97-7 


33-7 


96-7 


34-7 


90-7 


23-7 


717 


21-7 


66-7 


23-7 


Cardross 










- 


42-0 


- 


40-0 


- 


36-5 


- 


27-0 


- 


22-0 


- 


23-0 


Balloch Castle 










121-0 


34-0 


ipi-o 


32-0 


95-0 


27-0 


78-0 


22-0 


- 


18-0 


_ 


20 


Cairndow 










134-5 


33-0 


132-3 


32-6 


113-9 


34-2 


112-9 


28-4 


87-6 


17-6 


74-2 


21-8 


Callton Mor 










115-0 


38-0 


95-1 


35-0 


90-0 


32-0 


76-1 


25-6 


- 


- 


63-0 


25-0 


Eallabus . 










119-5 


_ 


102-8 


- 


105-0 


- 


99-1 


- 


79-5 


- 


74-4 


_ 


Paisley . 










104-0 


34-0 


89-5 


29-4 


82-5 


31-4 


74-5 


23-2 


65-5 


18-4 


61-5 


18-4 


Glasgow . 










133-2 


37-1 


129-1 


34-1 


118-3 


32-2 


98-0 


23-4 


83-0 


16-4 


67-8 


18-7 


Douglas Castle 










112 


36-0 


97-0 


32-0 


100-0 


28-0 


89-0 


19-0 


78-0 


15-0 


66-0 


21-0 


Smeaton 










128-0 


31-0 


113-0 


32-0 


105-0 


27-0 


95-0 


23-0 


88-0 


16 


67-0 


20-0 


Thurston 










1150 


35-0 


102-0 


35-0 


97-0 


34-0 


94-0 


32-5 


77-0 


25 


58-0 


26-0 


Thirlestane Castle . 








135-0 


28-0 


119-0 


20-0 


118-0 


20-0 


113-0 


17-0 


94-0 


12-0 


85-0 


10-0 


South Cairn . 








88-0 


42-0 


75-0 


43-0 


75-0 


40-0 


- 


- 


- 


- 


- 


- 




2491-2 


751-5 


2268-8 


746-3 


2264-3 


675-4 


1972-6 


543-9 


1479-6 


412-3 


1238-4 


461-9 




-=-22 


-=-22 


-=-22 


-=-23 


-=-23 


-=-23 


-^-21 


-=-23 


-=-19 


-f22 


-=-19 


-=-23 


Means 


113-2 


34 - 2 


103-1 


3 2 '4 


98-4 


29-4 


93 '9 


23-6 


77 '9 


187 


65-2 


20*1 





July. 


August. 


September. 


October. 


November. 


December. 


1867. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick ..... 


98-0 


26-0 


101-0 


28-0 


92-3 


29-5 


71-2 


26-8 


59-5 


26-7 


54-2 


22-0 


Kirkwall 










- 


_ 


87-6 


28-9 


88-8 


30-4 


61-1 


22-4 


- 


14-8 


- 


20-4 


Stornoway 










95-0 


- 


94-0 


- 


88-0 


21-0 


74-0 


22-0 


63-0 


21-0 


- 


- 


Culloden 










119-8 


38-8 


117-0 


36-6 


102-0 


33-7 


88-0 


28-2 


69-8 


26-7 


55-0 


22-1 


Portree . 










119-7 


28-0 


119-0 


30 


- 


30 


- 


25-2 


- 


- 


- 


18-8 


Elgin 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Castle Newe 










100-0 


30-0 


107-0 


28-0 


94-0 


26-0 


96-0 


21-0 


85-0 


19-0 


69-0 


19-0 


Braemar . 










- 


- 


105-0 


37-6 


98-0 


31-8 


- 


24-3 


- 


25 3 


- 


19-0 


Aberdeen 










94-0 


28-5 


100-7 


27-5 


99-0 


24-8 


96-5 


14-5 


85-2 


13-0 


69-0 


12-0 


Banchory 










100-0 


26-0 


99-0 


28-0 


100-0 


25-0 


- 


- 


77-0 


12-0 


64-0 


13-0 


Kettins . 










_ 


36 


- 


41-0 


- 


32-0 


- 


24-0 


- 


24-0 


- 


18-0 


Perth . 










- 


_ 


120-0 


36-0 


- 


- 


- 


- 


- 


22-0 


- 


19-0 


Nookton 










117-0 


31-4 


121-0 


34-4 


103-0 


29-4 


89-0 


18-4 


77-0 


20-4 


58-0 


16-4 


Dollar . 










99-7 


31-7 


- 


- 


947 


34-7 


88-7 


26-7 


84-7 


24-7 


65-7 


20-7 


Cardross 










- 


38-0 


- 


42-0 


- 


35-0 


- 


27-0 


- 


25-0 


- 


22-5 


Balloch Castle 










114-0 


32-0 


107-0 


35-0 


94-0 


25-0 


72-0 


20-0 


- 


- 


- 


- 


Cairndow 










133-2 


30-4 


122-4 


38-0 


116-8 


31-2 


103-1 


24-7 


96-4 


22-6 


76-7 


21-9 


Callton Mor 










114-0 


34-0 


117-0 


37-8 


95-0 


36-5 


83-5 


24-0 


61-8 


21-2 


- 


- 


Eallabus 










121-0 


_ 


119-0 


- 


97-0 


_ 


86-5 


- 


74 


- 


50-0 


_ 


Paisley . 










98-5 


33-8 


89-5 


30-4 


87-5 


32-0 


76-5 


24-4 


73-5 


19-8 


62-3 


14-8 


Glasgow 










134-7 


33-5 


134-0 


38-5 


114-0 


29-1 


97-2 


22-8 


75-5 


16-1 


57-5 


15-5 


Douglas Castle 










109-0 


33-5 


101-0 


40-0 


91-0 


28-0 


86-0 


22 


80-0 


17-0 


61-0 


10-0 


Smeaton 










119-0 


30-0 


120-0 


37-0 


110-0 


28-0 


89-0 


22-0 


80-0 


20-0 


61-0 


150 


Thurston 










106-0 


39-5 


110-0 


44-0 


98-0 


41-5 


89-0 


26-0 


80-0 


27-0 


65-0 


22-5 


Thirlestane Castle . 








126-0 


34-0 


119-0 


26-0 


120-0 


21-0 


111-0 


13-0 


102-0 


18-0 


86-0 


12-0 


South Cairn . 








112-0 


42-0 


112-0 


44-0 


100-0 


38-0 


85-0 


32-0 


70-0 


25-0 


560 


25-0 




2230-6 


657-1 


2422-2 


768-7 


2083-1 


693-6 


1643-3 


511-4 


1394-4 


461-3 


1010-4 


379-6 




-=-20 


-f20 


-=-22 


-=-22 


-=-21 


-=-23 


-fl9 


-=-22 


-=-18 


-=-22 


-fl6 


-=-21 


Means 


ni'S 


32 '9 


no'i 


34'9 


99-2 


30-2 


86 -s 


23-2 


77 '5 


21 '0 


63-2 


i8-i 



VOL. XXXV. PART 3. 



2 P 



238 



PROFESSOR C. PIAZZT SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1868. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick ..... 


56-2 


17-7 


58-4 


19-8 


69-2 


25-4 


85-2 


27-0 


93-4 


29-1 


91-2 


38-0 


Kirkwall 










18-5 


_ 


15-0 


- 


15-4 


77-7 


25-7 


88-7 


26-4 


100-1 


33 6 


Stornoway 








55-0 


13-0 


75-0 


18-0 


- 


- 


75-0 


- 


- 


- 


103-0 


- 


Oalloden 








65-4 


16-6 


77-2 


26-6 


100-8 


22-6 


105-0 


25-7 


108-1 


26-6 


130-3 


35-4 


Portree . 








_ 


- 


_ 


- 


- 


- 


- 


21-0 


- 


25 


- 


- 


Castle Newe . 








65-0 


6-0 


67-0 


23-0 


76-0 


17-0 


84-0 


24-0 


88-0 


22-0 


96-0 


28-0 


Braemar 








- 


12-5 


- 


23-0 


- 


17-2 


- 


22-3 


- 


25-0 


- 


32-0 


Aberdeen 








_ 


_ 


82-0 


18-8 


92-7 


18-6 


90-2 


18-6 


90-2 


18-6 


98-6 


27-2 


Banchory 








59-0 


9-0 


78-0 


14-0 


92-0 


15-0 


87-0 


17-0 


95-0 


16-0 


96-0 


27-0 


Kettins . 








- 


13 


- 


24-0 


- 


20-0 


- 


25-0 


- 


27-0 


- 


33-0 


Perth . 








62-0 


12-0 


75-0 


22-0 


110-0 


18-0 


90-0 


19-0 


103-0 


24-0 


123-0 


31-0 


Nookton 








64-0 


12-4 


75-0 


17-4 


86-0 


16-0 


102-0 


19-4 


105-0 


19-4 


123-0 


31-4 


Dollar . 








64-0 


18-0 


- 


- 


86-7 


24-7 


- 


- 


- 


- 


99-7 


35-7 


Cardross 








- 


20-0 


_ 


25-0 


- 


24-5 


- 


23-0 


- 


28-0 


- 


38-0 


Balloch Castle 








- 


- 


60-0 


23-0 


74-0 


20-0 


96-0 


18-0 


106-0 


20-0 


123-0 


32-0 


Cairndow 








84-7 


- 


95-4 


24-8 


109-5 


26-0 


129-4 


23-0 


125-7 


27-5 


132-4 


30-4 


Callton Mor . 










- 


57-0 


24-0 


78-2 


25-0 


- 


- 


102-0 


27-2 


117-0 


35-0 


Paisley . 








66-1 


16-4 


68-5 


21-4 


71-5 


27-2 


73-5 


21-6 


82-8 


23-0 


102-2 


34-2 


Auchendrane . 








- 


_ 


_ 


_ 


- 


- 


- 


_ 


- 


_ 


- 


_ 


Glasgow 








75-7 


16-3 


89-7 


19-5 


115-7 


18-7 


119-5 


19-2 


123-1 


26-7 


135-4 


37-0 


Douglas Castle 








71-0 


15-0 


65 


23-0 


94-0 


18-0 


90-0 


19-0 


98-0 


23-0 


107-0 


310 


Smcaton 








62-0 


13-0 


85-0 


21-0 


90-0 


15-0 


100-0 


17-0 


101-0 


170 


116-0 


30 


Thurston 








59-0 


21-0 


67-0 


24-5 


82-0 


22-0 


82-0 


26-5 


92-0 


26-0 


111-0 


38-0 


Thirlestane Castle 








77-0 


9-0 


91-0 


14-0 


109-0 


15-0 


111-0 


18-0 


1190 


150 


115-0 


28-0 


South Cairn . 








54-0 


22-0 


60-0 


28-0 


68-0 


29-0 


82-0 


28-0 


88-0 


32-0 


92-0 


40-0 




1040-1 


281-4 


1326-2 


469-8 


1605-3 


450-3 


1679-5 


458-0 


1809-0 


524-5 


2211-9 


725-9 




-=-16 


-4-19 


■v-18 


-1-22 


-rl8 


-4-22 


•4-18 


-4-21 


-4-18 


-4-22 


-4-20 


-4-22 


Means 


65-0 


14-8 


737 


21 - 4 


89-2 


20 -5 


; 93 "3 


21-8 


100-5 


23 '9 


no'6 


33'° 



1869 








January. 


February. 


March. 


April. 


Ma 


y- 


June. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick ..... 


54-2 


22-3 


68-0 


24-0 


75-9 


20-8 


84-2 


11-0 


85-0 


19-0 


93-4 


26-5 


Kirkwall 








_ 


20-4 


64-6 


12-4 


76-8 


20-0 


95-8 


15-0 


82-6 


13-9 


85-5 


25-4 


Stornoway 








58-0 


_ 


65 


19 


82-0 


- 


84-0 


14-0 


83-0 


_ 


95-0 


_ 


Cnlloden 








69-0 


20-1 


84-1 


24-6 


96-0 


17-6 


112-0 


18-0 


1117 


24-6 


112-9 


27-8 


Castle Newe . 








65-0 


10-0 


69-0 


25-0 


81-0 


17-0 


97-0 


20-0 


90-0 


12-0 


99-0 


26-0 


Braemar 








- 


15-3 


_ 


21-8 


- 


17-0 


- 


21-0 


_ 


20-6 


_ 


26-2 


Aberdeen 








73-3 


21-2 


85-0 


25-6 


78-4 


22-8 


89-3 


23-8 


85-3 


23-2 


94-0 


340 


Kettins . 








_ 


8-0 


_ 


25-0 


- 


120 


- 


15 


_ 


22-0 


_ 


26-0 


Perth . 








65-0 


13-0 


79-0 


21-0 


94-0 


13-0 


- 


- 


110-0 


20-0 


120 


27 


Nookton 








58-0 


19-4 


76-0 


23-4 


96-0 


15-4 


104-0 


16-4 


103-0 


19-4 


1130 


26-4 


Dollar . 








54-7 


25-7 


70-7 


26-7 


82-7 


23-7 


103-7 


22-7 


92-7 


267 


97 


34-7 


Cardross 








_ 


24-0 


_ 


30-0 


_ 


25-0 


- 


26-0 


_ 


29-0 


_ 


32-0 


Balloch Castle 








_ 


20-0 


- 


25-0 


90-0 


17-0 


- 


- 


110-0 


22-0 


121-0 


23-0 


Cairndow 








76-4 


19 


85-1 


26-2 


112-9 


16-9 


131-8 


21-3 


137-0 


21-3 


131-5 


24-8 


Callton Mor . 








52-0 


24-0 


620 


25-0 


83-0 


19-8 


109-0 


23-0 


107-0 


25-0 


118-0 


28-5 


Eallabus 








_ 


- 


- 


- 


- 


- 


100-5 


18-0 


102-0 


23-0 


111-5 


21-0 


Paisley . 








62-8 


17-4 


79-5 


25-4 


80-7 


15-4 


90-5 


14-9 


91-5 


20-4 


94-1 


20-4 


Auchendrane 








61-0 


21-0 


69-0 


28-0 


76-0 


20-0 


109-0 


23-0 


113-0 


19-0 


122-0 


26-0 


Glasgow 








76-8 


21-5 


88-3 


22-4 


103-8 


20-0 


114-5 


23-5 


1191 


24-2 


140-1 


29-4 


Douglas Castle 








59-0 


14-0 


78-0 


25-0 


80-0 


15-0 


102-0 


19-0 


101-0 


17-0 


102-0 


25-0 


Smeaton 








70-0 


15-0 


82-0 


21-0 


90-0 


17-0 


105-0 


14-0 


104-0 


18-0 


116-0 


22-0 


Thurston 








63-0 


22'5 


73-0 


26-5 


75-0 


25-0 


97-0 


23-0 


93-0 


27-5 


102-0 


32-0 


Thirlestane Castle 








73 


15-0 


91-0 


21-0 


98-0 


15-0 


1120 


19-0 


109-0 


18-0 


117-0 


27-0 


South Cairn . 








56-0 


27-0 


58-0 


28-0 


60-0 


25-0 


90-0 


28-0 


85-0 


30-0 


98-0 


36-0 




1147-2 


415-8 


14273 


552-0 


1712-2 


410-4 


1931 3 


429-6 


21149 


495-8 


2283-0 


633 1 




-=-18 


-4-22 


-fl9 


-4-23 


-4-20 


-4-22 


-4-19 


-4-22 


-4-21 


-4-23 


-4-21 


-4-23 


Means 


637 


18 -9 


75 "i 


24-0 


8 S -6 


187 


ioi'6 


i9"5 


1007 


21 - 6 


1087 


27 '5 



MEAN SCOTTISH METEOROLOGY. 



239 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPAKATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1868. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


103-2 


37-8 


90-7 


35-8 


85-6 


34-2 


72-2 


23 


54-2 


14-0 


52-4 


18-0 


Kirkwall 








100-7 


36-1 


88-8 


23-4 


81-5 


30-4 


67-5 


22-6 


- 


13-4 


_ 


15-4 


Stornoway 








98-0 


- 


100-0 


12-0 


88-0 


23-0 


82-0 


- 


62-0 


15-0 


- 


- 


Culloden 








123-8 


38-6 


125-0 


37-4 


107-2 


30-6 


83-8 


23-6 


65-0 


17-4 


55-8 


18-6 


Portree . 








- 


31-2 


- 


- 


- 


24-8 


- 


- 


- 


- 


_ 


_ 


Castle Newe . 








104-0 


30-0 


110-0 


31-0 


91-0 


29-0 


85-0 


21-0 


69-0 


18-0 


63-0 


18-0 


Braemar . 








- 


33 


- 


35-0 


- 


28-0 


- 


22-8 


- 


190 


_ 


18-3 


Aberdeen 








104-3 


26-9 


127-3 


27-6 


103-5 


35-1 


92-3 


24-1 


74-0 


25-9 


73-8 


22-9 


Banchory 








- 


- 


- 


- 


100-0 


22-0 


92-0 


12-0 


- 


- 


_ 


- 


Kettins . 








- 


- 


- 


38-0 


- 


28-0 


- 


22-0 


- 


18-0 


_ 


15-0 


Perth . 








125-0 


36-0 


128-0 


34 


120-0 


31-0 


94-0 


19-0 


73-0 


15-0 


63 


15-0 


Nookton 








120-0 


36-4 


1260 


35-4 


118-0 


26-4 


86-0 


18-4 


74-0 


15-4 


54-0 


17-4 


Dollar . 








107-7 


41-7 


114-7 


39-7 


104-7 


34-7 


91-7 


27-0 


777 


22-7 


57 


22-0 


Cardross 








- 


41-0 


- 


45-0 


- 


32-0 


- 


25-0 


- 


20-0 


_ 


26-0 


Balloch Castle 








126-0 


35 


119-0 


37-0 


102-0 


24-0 


80-0 


15-0 


57-0 


10-0 


_ 


_ 


Cairndow 








143-4 


37-1 


135 1 


36-0 


130-8 


27-7 


125-8 


23-7 


91-3 


13-6 


75-4 


16-3 


Callton Mor . 








123-5 


36-8 


109-0 


37-0 


95-5 


30-1 


75-0 


25-0 


54-2 


18-2 


53-5 


19-5 


Paisley . 








- 


_ 


106 


40-6 


91-6 


26-4 


77-5 


20-9 


72-5 


14-3 


64-5 


16-6 


Auchendrane 








- 


- 


- 


- 


- 


- 


79-0 


24-0 


60-0 


19-0 


53-0 


20-0 


Glasgow 








141-3 


39-5 


129-7 


41-3 


116-9 


31-1 


90-3 


24-0 


75-1 


16-3 


66-7 


21-2 


Douglas Castle 






• 


112-0 


33-0 


115-0 


36-0 


92-0 


25-0 


89-0 


19-0 


72-0 


12-0 


63-0 


15 


Smeaton 








117-5 


34-0 


116-0 


37-0 


102-0 


31-0 


91-0 


18-0 


75-0 


16-0 


70-0 


15-0 


Thurston 








112-0 


41 


115-0 


44-0 


107-0 


36-0 


91-0 


27-0 


71-0 


25-0 


64-0 


23-5 


Thirlestane Castle 








121-0 


25-0 


126-0 


31-0 


112-0 


26-0 


87-0 


19-0 


81-0 


18-0 


75-0 


10-0 


South Cairn . 








125-0 


45-0 


120-0 


44-0 


90-0 


35-0 


72-0 


33-0 


58-0 


26-0 


64-0 


28-0 




2108-4 


715-1 


2201-3 


778-2 


2039-3 


701-5 


1804-1 


509-1 


1316-0 


402 2 


1068-1 


3917 




■i-18 


-=-20 


-=-19 


-=-22 


-f20 


-=-24 


-=-21 


-7- 23 


-=-19 


-t-23 


■7-17 


-=^21 


Means 


117-1 


35-8 


"5 '9 


3S"4 


102 - 


29-2 


8S-9 


22 - I 


69 '3 


17 "5 


62-8 


187 





July. 


August. 


September. 


October. 


November. 


December. 


1869. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


96-2 


38-5 


90-7 


30-0 


87-0 


26-2 


76-0 


23-1 


58-6 


15-0 


49-7 


11-3 


Kirkwall 








94-0 


39-9 


87-6 


31-4 


84-2 


25-4 


68-6 


22-4 


- 


23-4 


_ 


13-9 


Stornoway 








- 


- 


84-0 


- 


86-0 


5-0 


84-0 


- 


62-0 


17-0 


47-0 


15-0 


Culloden 








117-2 


37-1 


118-0 


33-1 


107-0 


311 


107-0 


22-6 


79-8 


9-6 


58-0 


7-8 


Castle Newe . 








104-0 


32-0 


102-0 


26-0 


89-0 


29-0 


100-0 


23-0 


74-0 


9-0 


610 


-5-0 


Braemar . . 








- 


30-8 


- 


21-2 


- 


23 


- 


18-0 


- 


7-0 


- 


1-0 


Aberdeen 








100-0 


380 


109-3 


28-6 


119-0 


32-0 


115-7 


27 


85-7 


17-1 


67-2 


16-5 


Kettins . 








- 


340 


- 


24-0 


- 


30-0 


- 


21-0 


- 


12 


_ 


3 


Perth . 








138-0 


35-0 


128-0 


26-0 


1130 


32-0 


103-0 


20-0 


58-0 


120 


_ 


_ 


Nookton 








116-0 


34-4 


112 


23-4 


103 


23-4 


90-0 


15-0 


77-0 


13-4 


51-0 


4-4 


Dollar . 








1177 


38-7 


115-0 


30-8 


104-0 


36-8 


- 


- 


- 


_ 


68-0 


15-0 


Cardross 








- 


46 


- 


31-9 


- 


35-5 


- 


26-5 


- 


21-0 


- 


17-4 


Balloch Castle 








124-0 


34-0 


117-0 


25-0 


110-0 


30-0 


83-0 


19-0 


58-0 


130 


48-9 


5-0 


Cairndow 








133-5 


35-5 


134-5 


34-5 


117-6 


25-1 


109-1 


18-0 


86-2 


10-2 


77-6 


6-6 


Callton Mor . 








115-0 


39-0 


105-0 


29-1 


109-9 


36-5 


78-2 


24-0 


69-9 


18-1 


53-0 


8-2 


Eallabus 








109-0 


25-5 


104-0 


16-9 


90-5 


23 


84-0 


_ 


59-0 


_ 


48-0 


_ 


Paisley . 








987 


34-6 


103-5 


22-9 


96-0 


31-4 


88-0 


21-4 


- 


15-4 


- 


7-0 


Auchendrane 








124-0 


38-0 


112-0 


24-0 


107-0 


29-0 


91-0 


20-0 


66-0 


14-0 


530 


10-0 


Glasgow 








134-6 


40-6 


136-2 


28-5 


127-9 


33-6 


91-9 


21-0 


64-9 


12-5 


66-6 


77 


Douglas Castle 








113-0 


35-0 


115-0 


21-0 


89-0 


310 


110-0 


18-0 


78-0. 


10-0 


71-0 


6-0 


Smeaton 








110-0 


340 


117-0 


22-0 


100-0 


27-0 


100-0 


20-0 


76-0 


10-0 


60-0 


8-0 


Thurston 








- 


- 


109-0 


33-0 


97-0 


36-0 


97-0 


29-0 


67-0 


20-0 


54-0 


20-0 


Thirlestane Castle . 








117-0 


31-0 


120-0 


21-0 


98-0 


29-0 


95-0 


23-0 


80-0 


14-0 


81-0 


13-0 


South Cairn . 








110-0 


40-0 


115-0 


25-0 


80-0 


35-0 


82-0 


32-0 


60 


25 


56 


20-0 




2171-9 


791-6 


2334-8 


609-3 


2115-1 


696-0 


1853-5 


464-0 


1260-1 


318-7 


1071-0 


211-8 




-=-19 


-=-22 


■7-21 


-=-23 


-=-21 


-=-24 


-v-20 


-=-21 


-=-18 


-=-22 


t-18 


-=-22 


Means 


"4 "3 


36-0 


III - 2 


26-5 


100-7 


29-0 


92-7 


22*1 


70-0 


i4'S 


59 - S 


9-6 



•_>40 



PROFESSOR C. PIAZZI SMYTH ON 



Tun i: XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


M 


iy. 


June. 


1870. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


543 


20-5 


66 2 


13-6 


75-1 


19-3 


81-2 


31-7 


93-2 


28-5 


102-2 


31-3 


Kirkwall 










- 


21-9 


_ 


17-0 


_ 


177 


81-1 


28-9 


83-5 


24-4 


92-8 


29-4 


Stornoway 










50-0 


16-0 


57-0 


7-0 


79-0 


5-0 


85-0 


- 


87-0 


34-0 


89 


33-0 


Culloden 










72-6 


16-6 


82-0 


13-9 


96-0 


16-6 


113-8 


24-1 


119-8 


27-2 


119-8 


32-1 


Dunvegan 










- 


22 5 


_ 


12-0 


- 


17-0 


_ 


25-5 


_ 


29-0 


- 


32-0 


Castle Newe 










69-0 


13 


65-0 


7-0 


80-0 


160 


_ 


_ 


_ 


_ 


_ 


_ 


Braemar . 










61 


13-7 


75-0 


9-0 


101-0 


13-0 


112-3 


23-2 


120-0 


27-5 


128-3 


33-6 


Aberdeen 










72-6 


17 2 


91-0 


16-8 


100-3 


20-2 


_ 


_ 


140-8 


28-6 


148-2 


28-5 


Kettins . 










- 


12-0 


_ 


15-0 


- 


15-0 


_ 


24-0 


- 


28-0 


- 


34-0 


Perth . 










57-0 


15-0 


82-0 


12-0 


97-0 


14 


_ 


- 


- 


- 


126-0 


31-0 


Nookton 










65-0 


9-0 


75-0 


1-4 


93 


8-4 


101-0 


22-4 


1100 


23-4 


109-0 


29-4 


Dollar . 










67-7 


16-7 


77-0 


13-7 


- 


- 


957 


27-7 


99-7 


31-7 


104-7 


377 


Cardross 










- 


24-4 


_ 


16-0 


_ 


21-4 


_ 


29-0 


_ 


26-5 


_ 


42-0 


Balloch Castle 










50-0 


15-0 


65-0 


4-0 


77-0 


10-0 


89-0 


15-0 


102-0 


12-0 


115-0 


27-0 


Cairndow 










79 3 


17-5 


99-5 


9-5 


102-1 


16-3 


118-7 


25-2 


127-4 


21-0 


132-9 


34-2 


Callton Mor 










49-9 


13-5 


60 


12-0 


75-0 


18-9 


89-0 


23-0 


104-0 


19-5 


109-0 


38-0 


Eallabus . 










56-0 


23-0 


60-0 


20-0 


75 


20-0 


77-0 


25-4 


94-0 


_ 


100-2 


_ 


Greenock 










- 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


90-0 


32-0 


100-0 


40-0 


Paisley . 










69-5 


22-5 


80-0 


_ 


- 


_ 


94-5 


- 


95-0 


- 


97-0 


_ 


Auchendrane 










53-0 


16-0 


67-0 


14-0 


91-0 


17 


104-0 


25-0 


114-0 


23-0 


122-0 


40-0 


Glasgow . 










66-1 


17-9 


88-8 


7-8 


91-2 


16-0 


112-4 


25-6 


117-3 


25-7 


128-1 


37-9 


Douglas Castl* 










70-0 


15-0 


74-0 


100 


90-0 


14-0 


102 


22-0 


105 


23-0 


115-0 


36 


Smeaton 










70-0 


5-0 


73-0 


8 


83 


13-0 


100-0 


19-0 


110-0 


22-0 


114-0 


32-0 


Thurston 










59-0 


17-5 


72-0 


18-0 


81-0 


22 


96-0 


27-0 


103-0 


32-5 


102-0 


40-0 


Thirlestaue Castle 








85-0 


7-0 


_ 


1-0 


102-0 


13 


119 


18-0 


124-0 


24-0 


128-0 


34-0 


South Cairn . 








50-0 


18-0 


52-0 


16-0 


68-0 


19-0 


78-0 


26-0 


86-0 


26-0 


95-0 


36-0 




1327-0 


406-4 


1461-5 


274-7 


1656-7 


362-8 


1849-7 


487-7 


2225-7 


569-5 


2478-2 


789-1 




-=-21 


4-25 


-=-20 


-=-24 


-=-19 


4-23 


4-19 


-=-20 


4-21 


-=-22 


4-22 


4-23 


Means 


63-2 


16-3 


73 'i 


n- 4 


87-2 


15-8 


97 '4 


24 '4 


106 - o 


25 '9 


II2-6 


34 '3 





1871 








January. 


Febr 


nary. 


March. 


April. 


May. 


June. 




Mux. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick .... 


50-3 


165 


60-1 


26-8 


78-2 


21-5 


97-2 


18-3 


100-7 


24-5 


110-2 


25-5 


Kirkwall 










- 


18-9 


_ 


21-9 


66-0 


20-6 


- 


11-4 


_ 


12-4 


- 


22-4 


Stornoway 










50-0 


15-0 


64 


19-0 


86-0 


9-0 


86-0 


12-0 


102-0 


16 


104-0 


22-0 


Culloden 










77-0 


12-9 


88-0 


13-7 


_ 


_ 


110-0 


19-4 


_ 


_ 


118-1 


34-1 


Dunvegan 










- 


24-0 


_ 


18-0 


_ 


18-0 


- 


23-0 


- 


26-0 


- 


27-5 


Braemar 










60-0 


4-6 


75-3 


18-9 


104-0 


19-8 


110-0 


18-0 


123-3 


23-0 


120-3 


27 3 


Aberdeen 










66-0 


11-4 


99-0 


24-2 


114-0 


13-0 


130-3 


17-0 


138-0 


20-0 


138-3 


27-4 


Kettins . 










- 


10-0 


_ 


22 


_ 


15-0 


_ 


23-0 


_ 


24-0 


_ 


27-0 


Perth . 










62-0 


100 


88-0 


17-0 


_ 


_ 


_ 


_ 


- 


_ 


- 


- 


Nookton . 










57-0 


7-4 


75-0 


17-4 


93-0 


8-4 


97-0 


17-4 


119-5 


15-2 


111-5 


27 2 


Dollar . 










- 


- 


_ 


_ 


93-7 


21-7 


_ 


_ 


105-7 


19-7 


106-7 


36-7 


Cardross 










- 


22-0 


_ 


25-0 


_ 


21-0 


_ 


28-0 


- 


24-0 


- 


36-0 


Balloch CastU 










48-0 


15-0 


55-0 


18-0 


75-0 


18-0 


90-0 


21-0 


112-0 


25-0 


102-0 


28-0 


Cairndow 










76 T 


14-6 


93-5 


22-5 


112-7 


18-8 


114-3 


25-8 


125-7 


16-7 


141-0 


- 


Callton Mor 










48-5 


12 2 


68-5 


27-2 


84-0 


21-0 


95-0 


24-3 


100-0 


21-5 


109-2 


33-3 


Eallabus 










51-0 


20-5 


67-0 


30-8 


90-0 


16-5 


90-0 


26-5 


115-0 


22-8 


113 


26-3 


Greenock 










48-0 


21-5 


60-5 


26-0 


75-0 


21-0 


86-0 


26-0 


_ 


27-0 


- 


- 


Paisley . 










64-0 


- 


75-5 


_ 


88-0 


_ 


83-5 


_ 


106-5 




98-5 


- 


Auchendrane 










51-0 


110 


74-0 


14-0 


93-0 


13-0 


102-0 


22-0 


1190 


21-0 


125-0 


30-0 


Glasgow . 










59-6 


14 1 


82-0 


20-0 


97-7 


110 


117-5 


23-4 


132-8 


21-1 


131-0 


32-2 


Douglas Castl 


B 








71-0 


7-0 


72-0 


12-0 


113-0 


11-0 


93-0 


15-0 


106-0 


16-0 


115-0 


25-0 


Smeaton 










64-0 


7-0 


76-0 


19-0 


96-0 


12-0 


93-0 


15-0 


112-0 


17-0 


103-0 


29-0 


Thurston 










760 


17-0 


79-0 


28-0 


95-0 


23-0 


96-0 


25-0 


103-0 


26-0 


100-0 


34-0 


Thirlestane Castle 








90-0 


3 


93-0 


20-0 


120-0 


12-0 


120-0 


16-0 


129-0 


19-0 


129-0 


26-0 


South Cairn . 








48-0 


15-0 


56-0 


24-0 


72-0 


24 


74-0 


26-0 


86 


23-0 


no-o 


30-0 




1217 5 


310-6 


1501 -4 


485-4 


1846-3 


369-3 


1884-8 


453-5 


2036-2 


460-9 


2185-8 


606-9 




-=-20 


-=-23 


-=-20 


4-23 


4-20 


4-22 


4-19 


4-22 


4-18 


4-22 


4-19 


4-21 


MEANS 


60-9 


!3'S 


75'i 


21*1 


92-3 


16-8 


99 '2 


20 - 6 


113-1 


21 -o 


115-0 


28*9 



MEAN SCOTTISH METEOROLOGY. 



241 



Table XXVIa. continued. —BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES, 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





187C 


). 






July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min, 


Sandwick 


99-4 


42-9 


106-7 


32-5 


92-0 


33-5 


90-2 


24-7 


58-9 


21-5 


52-9 


6-0 


Kirkwall 










98-4 


33-0 


104-4 


27-0 


80-7 


23-4 


66-9 


21-4 


56-3 


20-0 


_ 


7-2 


Stornoway 










97-0 


40-0 


105-0 


29-0 


89-0 


21-0 


87-0 


22-0 


64-0 


16-0 


48-0 


6-0 


Culloden 










125-0 


35-6 


125-8 


34-0 


111-2 


26-6 


105-0 


21-6 


83-4 


15-6 


50-4 


7-0 


Dunvegan 










- 


33-6 


- 


37-0 


- 


27-5 


- 


23-2 


- 


18-0 


_ 


10-0 


Castle Newe 










- 


- 


- 


_ 


- 


- 


- 


_ 


_ 


_ 


_ 


_ 


Braemar 










128-3 


31-0 


132-0 


36-8 


116-0 


25-0 


112-5 


23-0 


71-0 


20-2 


63-7 


o-o 


Aberdeen 










145-3 


34-5 


133-0 


30-1 


125-6 


27-4 


108-3 


23-0 


81-9 


19-1 


67-2 


4-0 


Kettins . 










- 


34-0 


- 


34-0 


- 


30-0 


- 


26-0 


_ 


20-0 


_ 


o-o 


Perth . 










135-0 


32-0 


132-0 


32-0 


112-0 


24-0 


92-0 


20-0 


82-0 


18-0 


56-0 


2-0 


Nookton 










126-0 


33-4 


113-0 


32-4 


103-0 


28-4 


94-0 


19-4 


85-0 


14-4 


52-0 


7-4 


Dollar . 










124-7 


39-7 


1177 


35-7 


107-7 


33-7 


109-7 


28-7 


91-3 


22-7 


70-7 


3-7 


Cardross 










- 


40-4 


_ 


35-4 


- 


34-0 


- 


29-4 


_ 


25-0 


_ 


10-0 


Ballooh Castle 










- 


- 


- 


- 


- 


- 


- 


26-0 


65-0 


18-0 


50-0 


7-0 


Cairndow 










140-3 


33-0 


137-2 


28-8 


- 


- 


119-1 


25-2 


98-5 


16-6 


89-9 


8-0 


Calrton Mor 










109-0 


35-0 


112-0 


32-0 


97-0 


28-0 


84-0 


25-2 


64-0 


21-0 


50-0 


8-0 


Eallabus 










104-5 


36-0 


117-5 


39-4 


99-0 


_ 


89-2 


_ 


69-0 


21-2 


65-0 


11-0 


Greenock 










99-0 


39-5 


109-0 


31-0 


87-5 


30-0 


75-0 


27-0 


61-5 


21-0 


56-0 


14-5 


Paisley . 










110-5 


- 


no-o 


- 


96-0 


- 


78-0 


- 


73-5 


_ 


66-0 


_ 


Auchendrane . 










119-0 


39-0 


118-0 


31-0 


101-0 


33-0 


97-0 


24-0 


66-0 


17-0 


50-0 


7-0 


Glasgow 










128-0 


43-0 


130-0 


32-2 


117-8 


30-8 


92-5 


25-5 


80-1 


19-0 


57-5 


-5-0 


Douglas Castlt 










123-0 


37-0 


120-0 


29-0 


109-0 


25-0 


115-0 


24-0 


91-0 


14-0 


70-0 


3-0 


Smeaton 










121-0 


31-0 


114-0 


27-0 


107-0 


22-0 


100-0 


19-0 


83-0 


15-0 


63-0 


-1-0 


Thurston 










111-0 


41-0 


no-o 


40-0 


105-3 


34-0 


99-0 


31-0 


85-0 


24-0 


58-0 


11-0 


Thirlestane Castle 








136-0 


34-0 


134-0 


33-0 


115-0 


25-0 


114-0 


22-0 


107-0 


18-0 


90-0 


o-o 


South Cairn . 








110-0 


40-0 


115-0 


35-0 


78-0 


38-0 


85-0 


30-0 


66-0 


22-0 


56-0 


12-0 




2490-4 


838-6 


2496-3 


754-3 


2049-8 


600-3 


2013-4 


561-3 


1683-4 


457-3 


1282-3 


138-8 




-=-21 


-=-23 


-=-21 


-=-23 


-=-20 


-=-21 


-=-21 


-=-23 


•=-22 


-=-24 


-f-21 


-=-24 


Means 


n8-6 


36-5 


118-9 

1 


32-8 


102-5 


28-6 


95"9 


24-4 


76 '5 


19- 1 


6ri 


5-8 



1871 








July. 


August, 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


113-2 


34-7 


105-2 


30-9 


_ 


_ 


59-3 


21-0 


68-5 


18-3 


54-2 


14-5 


Kirkwall 








_ 


33-2 


_ 


30-4 


- 


21-4 


- 


24-6 


- 


19-4 


- 


19-4 


Stornoway 








106-0 


26-0 


107-0 


27-0 


103-0 


11-0 


85-0 


10-0 


65-0 


5-0 


53-0 


11-0 


Culloden 








121-8 


37-5 


119-5 


35-9 


115-8 


23-9 


96-5 


23-0 


83-0 


18-7 


61-9 


15-6 


Dunvegan 








- 


34-5 


_ 


36-5 


- 


16-5 


- 


19-7 


- 


18-0 


- 


20-0 


Braemar 








124-0 


30-2 


126-3 


31-3 


111-7 


23-7 


90-2 


20-2 


70-0 


16-0 


70-2 


11-8 


Aberdeen 








148-0 


34-5 


134-7 


30-0 


128-2 


24-7 


113-9 


22-1 


69-8 


18-3 


55-3 


14-5 


Kettins . 










36-0 


_ 


34-0 


_ 


26-0 


- 


24-0 


- 


18-0 


_ 


10-0 


Perth . 








_ 


_ 


_ 


_ 


_ 


_ 


96-0 


18-0 


78-0 


15-0 


63-0 


9-0 


Nookton 








120-5 


34-2 


120-5 


35-2 


105-5 


28-2 


89-5 


19-2 


67-5 


11-2 


50-5 


14-2 


Dollar . 








105-7 


42-7 


109-7 


40-7 


113-7 


32-7 


96-7 


26-7 


77-7 


19-7 


73-7 


14-7 


Cardross 








_ 


43-0 


_ 


41-0 


_ 


32-0 


- 


30 5 


- 


22-0 


- 


20-0 


Balloch Castle 








104-0 


34-0 


no-o 


32-0 


90-0 


20-0 


70-0 


18-0 


52-0 


12-0 


55-0 


10-0 


Cairndow 








132-8 


_ 


134-1 


_ 


_ 


- 


102-8 


_ 


90-9 


_ 


82-4 


_ 


Callton Mor . 








101-0 


33-0 


100-7 


37-2 


_ 


22-0 


- 


25-0 


- 


20-0 


- 


15-0 


Eallabus 








113-0 


32-0 


129-0 


31-0 


102-0 


22-1 


90-2 


23-8 


64-0 


18-2 


61-0 


14-5 


Greenock 








_ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


- 


- 


_ 


_ 


Paisley . 








- 


_ 


_ 


_ 


_ 


- 


- 


- 


- 


- 


- 


- 


Auchendrane . 








119-0 


39-0 


124-0 


38-0 


106-0 


27-0 


86-8 


24-0 


64-0 


16-0 


59-0 


13-0 


Glasgow . 








124-5 


39-2 


119-0 


36-7 


118-8 


25-3 


99-0 


23-0 


84-5 


14-3 


71-5 


17-5 


Douglas Castle 








101-0 


34-0 


125-0 


34-0 


110-0 


22-0 


86-0 


18-0 


75-0 


12-0 


68-0 


11-0 


Smeaton 








109-0 


34-0 


no-o 


34-0 


103-0 


28-0 


84-0 


20-0 


74-0 


16-0 


57-0 


15-0 


Thurston 








101-0 


42-0 


112-0 


40-0 


106-0 


35-0 


92-0 


26-0 


89-0 


21-0 


61-0 


23-0 


Thirlestane Castle 








127-0 


32-0 


134-0 


32-0 


125-0 


25-0 


115-0 


18-0 


99-0 


11-0 


88-0 


14-0 


South Cairn . 








90-0 


39-0 


92-0 


38-0 


88-0 


28-0 


74-0 


25-0 


58-0 


24-0 


58-0 


20-0 




2061-5 


744-7 


2112-7 


725-8 


1628-7 


494-5 


1626-1 


479-8 


1329-9 


364-1 


1142-7 


327-7 


1 -=-18 


H-21 


-fl8 


-=-21 


-=-15 


-=-20 


-t-18 


-=-22 


-=-18 


•=-22 


-fl8 


-=-22 


Means . . .1 114-5 


35 \5 


117-4 


34 '6 


108-4 


247 


9° '3 


21-8 


73 "9 


16-6 


63 - 5 


14-9 



VOL. XXXV. PART 3. 



2 Q 



242 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXYIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


Ap 


ril. 


May. 


June. 


1872. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick ..... 


55 


20-5 


71-2 


19-5 


86-2 


18-6 


87-0 


22-9 


96-4 


13-5 


117-0 


26-5 


Kirkwall 








- 


23-4 


63-7 


20 9 


80-2 


12-4 


96-0 


19-4 


98-4 


23-4 


108-0 


30-0 


Stornoway 








57-0 


8-0 


66-0 


17-0 


84-0 


17-0 


82-0 


- 


83-0 


18 


106-0 


25-0 


Culloden 








84-0 


20-6 


90-8 


20-6 


98-2 


16-1 


107-0 


25-6 


115-0 


27-1 


123-0 


33-4 


Dunvegau 








- 


21-0 


- 


20-0 


- 


15-0 




25-0 




- 


- 




Braemar 








66-2 


14-3 


70-2 


20-2 


104-0 


15-3 


105-6 


25-7 


117-3 


26-0 


124-8 


32-3 


Aberdeen 








68-2 


17-7 


104-0 


19-4 


107-5 


23-1 


120-0 


23-1 


136-0 


24-6 


143-4 


28-4 


Kettins . 








- 


20 


- 


22-0 


- 


22-0 


- 


22-0 


- 


- 


_ 


36-0 


Nookton . 








57-5 


17-2 


72-5 


19-2 


91-5 


17-2 


92"5 


21-2 


96-5 


22-2 


109-5 


29-2 


Dollar . 








71-7 


21-7 


74-7 


22-7 


90-7 


18-7 


91-7 


26-7 


90-0 


26-0 


104-7 


26-7 


Cardross 








- 


25-0 


- 


27-0 


- 


23-0 


- 


26-5 


- 


29-0 


- 


40-0 


Balloch Castle 








54-0 


22-0 


60-0 


20-0 


75-0 


17-0 


85-0 


18-0 


95-0 


20-0 


98-0 


27-0 


Cairndow 








791 


- 


96-6 


- 


105-9 


- 


112-1 


- 


119-9 


- 


120-8 


_ 


Callton Mor . 








- 


_ 


67-0 


31-5 


82-0 


19-5 


80-0 


25 


93-0 


21-0 


99-0 


34-0 


Eallabus 








57-0 


20-0 


67-0 


27-2 


84-5 


17-8 


96-5 


24-5 


102-0 


23-0 


109-5 


29-5 


Paisley . 








64-5 


21-5 


64-0 


25-7 


72-5 


19-0 


75-5 


22-0 


90-0 


25-7 


89-0 


31-0 


Auchendrane . 








60-0 


20-0 


71-0 


25-0 


80-0 


19-0 


99-0 


19-0 


115-0 


26-0 


122-0 


34-0 


Glasgow . 








80-9 


21-5 


88-6 


22-5 


101-2 


16-0 


113-4 


22-0 


119-5 


24-6 


122-0 


32-5 


Douglas Castle 








62-0 


14-0 


83-0 


25-0 


85-0 


14-0 


89-0 


22-0 


86-0 


23-0 


102-0 


32-0 


Smeaton . 








60-0 


11-0 


72-0 


17-0 


84-0 


14-0 


92-0 


21-0 


94-0 


15-0 


101-0 


21-0 


Thurston 








69-0 


23-0 


86-0 


27-0 


96-0 


25-0 


95-0 


30-0 


101-0 


31-0 


108-0 


37-0 


Thirlestane Castle . 








85-0 


10-0 


98-0 


17-0 


98-0 


20-0 


113-0 


25-0 


120-0 


20-0 


120-0 


25-0 


South Cairn . 








49-0 


22-0 


50-0 


28-0 


55-0 


20-0 


68-0 


24-0 


80-0 


26-0 


90-0 


28-0 




1180-1 


394-4 


1516-3 


492-4 


1761-4 


399-7 


1900-3 


490-6 


2048-0 


465-1 


2217-7 


638-5 




4-18 


-=-21 


4-20 


-=-22 


-f-20 


-=-22 


-=-20 


-=-21 


4-20 


+20 


-=-20 


4-21 


Means 


6 5 -6 


i8-8 


75-8 | 


22 "4 


88-i 


18-2 


95 'o 


23 '4 


102 '4 


23 '3 


1 10 -9 


3°"4 





January. 


February. 


March. 


ApriL 


May. 


June. 


1873. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


53-2 


20-5 


63-0 


10-1 


81-2 


20-7 


94-3 


19-0 


_ 


_ 


122-4 


25-5 


Kirkwall 








54-8 


21-9 


60-9 


2-9 


78-9 


22-4 


97-1 


19-7 


105-4 


12-4 


121-8 


25-4 


Stornoway 








55-0 


15 


63-0 


9-0 


84-0 


19-0 


85-0 


18-0 


88-0 


14-0 


98-0 


23-0 


Culloden 








- 


- 


93-2 


8-6 


- 


- 


- 


_ 


- 


_ 


_ 


_ 


Braemar 








69-0 


14-0 


63-7 


7-3 


95-2 


19-3 


115-0 


22-0 


124-8 


22-0 


127-0 


26-0 


Aberdeen 








70-0 


20-0 


91-7 


2-4 


101-5 


18-4 


117-0 


20-5 


140-3 


19-0 


134-8 


36-2 


Kettins . 








- 


16-0 


- 


4-0 


- 


24-0 


- 


24-0 


- 


24-0 


_ 


34-0 


Nookton 








55-5 


8-2 


73-5 


8-2 


84-5 


17-2 


101-5 


16-2 


104-5 


17-2 


117-5 


28-2 


Dollar . 








64-7 


16-7 


79-7 


10-7 


86-7 


19-7 


97-7 


19-7 


- 


- 


101-7 


34-7 


Cardross 








- 


25-0 


_ 


20-0 


- 


26-0 


- 


29-0 


- 


30-0 


_ 


39-0 


Balloch Castle 








50-0 


18 


65-0 


10 


67-0 


18-0 


98-0 


18-0 


107-0 


20-0 


no-o 


32-0 


Cairndow 








76-6 


- 


98-9 


- 


- 


- 


- 


- 


_ 


_ 


- 


_ 


Callton Mor . 








53-0 


13-0 


67-0 


15-0 


77-0 


23-0 


88-0 


21-0 


97-0 


25-0 


102-0 


32-0 


Eallabus . 








54-0 


17-5 


77-0 


11-5 


78-0 


21-0 


92-0 


19-0 


112-0 


22-0 


122-0 


28-0 


Paisley . 








65-0 


17-0 


78-0 


12-0 


75-5 


22-0 


99-5 


20-5 


94-5 


23-5 


96-0 


33-5 


Auchendrane . 








56-0 


10-0 


66-0 


13-0 


87-0 


20-0 


102-0 


19-0 


118-0 


22-0 


118-0 


33-0 


Glasgow . 








78-0 


19-0 


92-0 


10-0 


97-2 


20-1 


121-8 


21-2 


122-9 


23-2 


134-0 


30 


Douglas Castle 








86-0 


13-0 


91-0 


10-0 


105-0 


18-0 


126-0 


20-0 


108-0 


24 


111-0 


32 


Smeaton . 








66-0 


12-0 


69-0 


11-0 


78-0 


12-0 


87-0 


160 


93-0 


15-0 


105-0 


23-0 


Thurston 








66 


22-0 


79-0 


19-0 


90-0 


20-0 


99-0 


27-0 


99-0 


27-0 


97-0 


37-0 


Thirlestane Castle 








87-0 


14-0 


102-0 


- 


104-0 


15-0 


120-0 


19-0 


128-0 


20-0 


120-0 


310 


South Cairn . 








52 


21-0 


64-0 


16-0 


58-0 


18-0 


75-0 


19-0 


86-0 


22-0 


95-0 


27-0 




1211-8 


333-8 


1537-6 


210-7 


1528-7 


393-8 


1815-9 


407-8 


1728-4 


382-3 


2033 2 


610-5 




4-19 


-=-20 


-=-20 


-=-20 


-=-18 


+20 


-=-18 


-=-20 


-=-16 


4-18 


-=-18 


-=-20 


Means 


63-8 


16-7 


769 


i°'5 


84-9 


197 


1 00 -9 


20 -4 


108 -o 


21 '2 


113-0 


3°'S 




MEAN SCOTTISH METEOROLOGY. 



243 



Table XXYIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PBEPAEATOEY TABLE FOE THE FEOST AND FIRE BETUENS OF TABLES XXVII., XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1872. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sand wick 


115-2 


33-1 


111-3 


29-5 


99-1 


26-3 


75-8 


22-5 


64-7 


18-4 


49-1 


17-5 


Kirkwall 








116-8 


31-5 


117-7 


30-4 


97-9 


24-2 


82-8 


23-9 


- 


- 


47-0 


18-9 


Stornoway 








106-0 


25-0 


100-0 


23-0 


95-0 


15-0 


72-0 


12-0 


63-0 


- 


51-0 


_ 


Culloden 








123-5 


32-5 


113-8 


33-9 


107-0 


28-4 


102-0 


22-8 


89-9 


20-7 


61-2 


16-9 


Dunvegan 








- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Braemar 








132-3 


32-0 


123-0 


31-3 


107-2 


29-9 


95-3 


20-6 


67-3 


18-3 


65-0 


5-0 


Aberdeen 








147-2 


33-4 


139-0 


29-0 


128-0 


27-8 


102-2 


23-6 


89-0 


19-0 


61-2 


16-0 


Kettins . 








- 


34-0 


- 


36-0 


- 


30-0 


_ 


22-0 


- 


24-0 


_ 


12-0 


Nookton 








124-5 


31-2 


111-5 


33-2 


103-5 


24-2 


81-5 


17-2 


70-5 


20-2 


56-5 


10-2 


Dollar . 








116-7 


37-7 


- 


- 


102-7 


27-7 


93-7 


21-7 


79-7 


23-7 


67-7 


15-7 


Cardross 








- 


41-0 


- 


42-0 


_ 


35-0 


- 


- 


- 


30-0 


- 


23-0 


Balloon Castle 








110-0 


28-0 


101-0 


25-0 


78-0 


18-0 


64-0 


15-0 


55-0 


21-0 


50-0 


16-0 


Cairndow 








144-4 


- 


138-6 


- 


- 


- 


- 


- 


- 


- 


74-4 


_ 


Callton Mor . 








105-0 


33-0 


114-0 


33-0 


90-0 


25-0 


78-0 


18-0 


69-0 


23-0 


57-0 


16-0 


Eallabus . 








122-4 


31-5 


114-0 


31-0 


96-0 


27-0 


79-0 


20-0 


73-0 


12-0 


52-0 


16-0 


Paisley . 








109 


33-0 


101-5 


32-0 


96-5 


26-0 


81-5 


19-0 


79-5 


24-0 


68-0 


14-5 


Auchendrane . 








118-0 


37-0 


110-0 


37-0 


108-0 


30-0 


82-0 


20-0 


61-0 


20-0 


52-0 


19-0 


Glasgow . 








131-0 


34-8 


132-2 


39-8 


116-6 


30-5 


102-8 


25-0 


86-2 


17-8 


69-0 


14-0 


Douglas Castle 








124-0 


31-0 


124-0 


33-0 


115-0 


23-0 


109-0 


15-0 


92-0 


14-0 


75-0 


17-0 


Smeaton 








111-0 


23-0 


103-0 


22-0 


90-0 


18-0 


85-0 


12-0 


76-0 


19-0 


66-0 


8-0 


Thurston 








114-0 


38-0 


104-0 


38-0 


95-0 


34-0 


.99-0 


27-0 


84-0 


28-0 


61-0 


22-0 


Thirlestane Castle 








130-0 


24-0 


128-0 


25-0 


111-0 


20-0 


106-0 


19-0 


98-0 


21-0 


80-0 


12-0 


South Cairn . 








98-0 


32-0 


86-0 


36-0 


- 


- 


72-0 


22-0 


54-0 


24-0 


50-0 


17-0 




2399-0 


676-7 


2171-6 


640-1 


1836-5 


520-0 


1663-6 


398-3 


1351-8 


398-1 


1213-1 


306-7 




-=-20 


-=-21 


-=-19 


-=-20 


-rl8 


-=-20 


-=-19 


-=-20 


-fl8 


-M9 


-=-20 


-=-20 


Means 


I20'0 


32 "2 


1 14 '3 


32-0 


102 -O 


26-0 


87-6 


19-9 


7S"i 


21 *o 


60 -7 


i5'3 





July. 


August. 


September. 


October. 


November. 


December. 


1873. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick ..... 


117-2 


38-3 


112-1 


30-5 


103-3 


30-5 


81-1 


30-4 


62-2 


21-6 


57-2 


24-5 


Kirkwall 










114-3 


32-4 


99-6 


26-4 


95-4 


28-0 


85-0 


26-7 


55-6 


18-4 


- 


18-7 


Stornoway 










103-0 


39-0 


101-0 


32-0 


97-0 


25-0 


92 


19-0 


65-0 


19-0 


56-0 


14-0 


Culloden 










- 


- 


- 


- 


111-1 


29-2 


98-0 


22-8 


81-8 


20-5 


72-3 


20-8 


Braemar 










124-2 


30-4 


121-0 


26-2 


115-0 


29-8 


95-2 


16-2 


68-8 


12-0 


77-8 


20-0 


Aberdeen 










129-2 


35-9 


137-5 


30-8 


135-5 


30-1 


- 


23-5 


- 


22-9 


- 


22-7 


Kettins . 










- 


40-0 


- 


38-0 


- 


- 


- 


- 


- 


- 


- 


- 


Nookton . 










128-5 


37-2 


103-5 


31-2 


106-5 


28-2 


91-5 


16-2 


67-5 


16-2 


57-5 


16-2 


Dollar . 










- 


- 


102-7 


37-7 


101-7 


29-7 


97-7 


19-7 


- 


- 


- 


- 


Cardross 










- 


43-0 


_ 


40-0 


_ 


30-5 


- 


23-5 


- 


23-0 


- 


24-5 


Balloch Castle 










114-0 


32-0 


95-0 


26-0 


98-0 


20-0 


75-0 


20-0 


53-0 


18-0 


54-0 


20-0 


Cairndow 










- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Callton Mor . 










99-0 


30-0 


98-0 


35-0 


95-0 


28-0 


78-0 


22-0 


64-0 


20-0 


53-0 


21-0 


Eallabus . 










111-0 


30-5 


106-5 


330 


103-0 


28-0 


91-0 


19-6 


67 


19-0 


57-0 


20-0 


Paisley . 










97-5 


30-5 


85-5 


31-5 


99-5 


26-0 


78-5 


20-0 


69-5 


22-0 


62-0 


21-0 


Auchendrane . 










121-0 


36-0 


110-0 


37-0 


98-0 


33-0 


84-0 


22-0 


59-0 


21-0 


53-0 


22-0 


Glasgow . 










131-2 


34-0 


126-7 


29-9 


113-6 


29-2 


88-2 


16-8 


80-7 


19-0 


67-0 


21-2 


Douglas Castle 










120-0 


35-0 


119-0 


34-0 


127-0 


28-0 


109-0 


18-0 


89-0 


14-0 


65-0 


19-0 


Smeaton 










115-0 


30-0 


97-0 


25-0 


107-0 


30-0 


92-0 


21-0 


85-0 


23-0 


70-0 


20-0 


Thurston 










115-0 


41-0 


97-0 


39-0 


96-0 


32-0 


86-0 


27-0 


87-0 


27-0 


62-0 


26 


Thirlestane Castle 










125-0 


32-0 


116-0 


26-0 


125-0 


22-0 


111-0 


18-0 


- 


- 


- 


19-0 


South Cairn . 










99-0 


30-0 


85-0 


31-0 


72-0 


28-0 


75-0 


18-0 


58-0 


18-0 


54-0 


18-0 




1964-1 


657-2 


1913-1 


640-2 


1999-6 


565-2 


1608-2 


420-4 


1113-1 


354-6 


917-8 


388-6 




-=-17 


-=-19 


-=-18 


-=-20 


-=-19 


-=-20 


-=-18 


-=-20 


-=-16 


-i-18 


■4-15 


-=-19 


Means 


"5 - S 


34 '6 


106-3 


32-0 


105-2 


28-3 


89-3 


21 "O 


69-6 


197 


6l '2 


20 -4 



244 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1874. 
































Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 




59-2 


22-0 


75-7 


20-3 


75'2 


24-5 


1052 


30-5 


105-1 


25-8 


_ 


_ 


Kirkwall 










_ 


20-4 


- 


14-4 


- 


21-4 


97-6 


24-6 


108-2 


19-2 


103-5 


31-6 


Stornoway 










51-0 


14-0 


77-0 


16-0 


89-0 


9-0 


107-0 


19-0 


90-0 


15-0 


104-0 


23-0 


Culloden 










87-1 


20-6 


86-0 


15-6 


- 


- 


- 


- 


110-5 


25-6 


118-1 


28-9 


Braemar 










73-8 


12-2 


78-6 


14-0 


113-8 


15-4 


119-0 


19-2 


120-0 


18-0 


131-0 


29-0 


Aberdeen 










- 


19-7 




21-6 




22-0 


- 


25-8 


- 


27-2 


- 


30-9 


Nookton 










62-5 


17-2 


73-5 


9-2 


90-5 


13-2 


100-5 


18-2 


98-5 


22-2 


119-5 


24-2 


Cardross 










- 


26-0 


- 


- 


- 


17-0 


- 


29-0 


- 


27-0 


- 


30-5 


Balloch Castle 










50-0 


20-0 


65-0 


15-0 


75-0 


12-0 


96-0 


24-0 


98-0 


26-0 


115-0 


28-0 


Callton Mor . 










60-0 


210 


68-0 


19-0 


73-0 


22-0 


92-0 


29-0 


97-0 


27-0 


102-0 


34-0 


Eallabus 










57-0 


23-0 


- 


- 


77-0 


20-0 


104-0 


23-5 


123-0 


21-0 


129-0 


27-5 


Paisley . 










62-5 


25-0 


67-5 


15-0 


74-5 


10-5 


97-5 


25-0 


98-0 


23-0 


99-5 


25-0 


Auchendrane . 










58-0 


25-0 


67-0 


15-0 


81-0 


13-0 


108-0 


20-0 


110-0 


22-0 


127-0 


28-0 


Glasgow 










74-0 


23-0 


91-3 


18-0 


92-4 


15-3 


106-7 


26-0 


110-7 


24-1 


105-0 


25-0 


Douglas Castle 










69-0 


20-0 


91-0 


17-0 


105-0 


14-0 


121-0 


24-0 


123-0 


20-0 


131-0 


25'0 


Smeaton 










79-0 


22-5 


85-0 


9-5 


93-0 


16-5 


101-0 


23-5 


96-0 


22-0 


107-0 


23-0 


Thurston 










79-0 


25-0 


89-0 


21-0 


92-0 


22-2 


106-0 


29-0 


94-0 


28-0 


102-0 


34-0 


Thirlestane Castle 










- 


21-0 


- 


10-0 


- 


13-0 


- 


20-0 


- 


16-0 


- 


22-0 


South Cairn . 










52-0 


22-0 


50-0 


18-0 


56-0 


15-0 


76-0 


20-0 


90-0 


20-0 


95-0 


27-0 




974-1 


399-6 


1064-6 


268-6 


1187-4 


296-0 


1537-5 


430-3 


1672-0 


429-1 


1688-6 


496-6 


-=-15 


4-19 


-=-14 


-=-17 


-=-14 


-5-I8 


-=-15 


t-18 


4-16 


■7-19 


■4-15 


-5-18 


Means 


64-9 


21 -O 


76 - o 


15-8 


84-8 


16 -4 


102-5 


23 "9 


i°4'S 


22 "6 


II2'6 


27-6 





January. 


February. 


March. 


ApriL 


May. 


June. 


1875. 
























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


57-2 


16-5 


64-2 


21-5 


79-2 


27-4 


94-0 


25-6 


_ 


_ 


_ 


_ 


Kirkwall 








- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Stornoway 








53-0 


15-0 


74-0 


11-0 


87-0 


14-0 


97-0 


18-0 


88-0 


20-0 


104-0 


20-0 


Braemar 








71-0 


15-4 


76-3 


5-0 


101-3 


17-2 


117-0 


19-8 


119-0 


29-0 


123-0 


28-8 


Aberdeen 








- 


12-5 


_ 


16-9 


- 


26-6 


- 


30-4 


_ 


30-5 


_ 


33-2 


Nookton 








55-5 


6-2 


65-5 


10-2 


88-5 


17-2 


101-5 


15-2 


104-5 


26-2 


100-5 


27-2 


Balloch Castle 








50-0 


8-0 


55-0 


12-0 


70-0 


15-0 


90-0 


15-0 


85-0 


30-0 


98-0 


30-0 


Callton Mor . 








55-0 


24-0 


64-0 


18-0 


81-0 


20-0 


91-0 


23-0 


89-0 


32-0 


95-0 


35-0 


Eallabus 








63-0 


24-0 


73-0 


15-0 


83-0 


16-0 


104-0 


20-5 


110-0 


26-5 


114-0 


28-5 


Paisley . 








66-5 


5-5 


72-5 


14-0 


70-5 


16-0 


91-5 


16-0 


90-5 


29-0 


100-5 


29-0 


Annanhill 








62-0 


18-0 


74-0 


20-5 


108-0 


19-0 


131-7 


23-5 


- 


- 


135-2 


37-0 


Glasgow 








59-5 


9-2 


60-8 


14-8 


73-2 


15-7 


83-9 


19-1 


89-9 


33-9 


86-9 


32-2 


Ridge Park 








- 


- 


_ 


_ 


_ 


_ 


- 


_ 


- 




104-0 


36-0 


Douglas Castle 








81-0 


14-0 


83-0 


16-0 


87-0 


15-0 


100-0 


17-0 


90-0 


28-0 


104-0 


30-0 


Smeaton 








75-0 


1-0 


75-0 


12-0 


85-0 


14-5 


102-0 


22-5 


113-0 


27-5 


105-0 


26-5 


Thurston 








73-0 


14-0 


74-0 


21-0 


80-0 


23-0 


105-0 


29-0 


97-0 


35-0 


106-0 


35-0 


Thirlestane Castle 








85-0 


12-0 


81-0 


7-0 


92-0 


15-0 


106-0 


14-0 


103-0 


18-0 


109-0 


20-0 




906-7 


195-3 


992-3 


214-9 


11857 


271-6 


1414-6 


308-6 


1178-9 


365-6 


1485-1 


448-4 




•4-14 


-5-15 


4-14 


-4-15 


-5-14 


-4-15 


4-14 


4-15 


4-12 


4-13 


-5-14 


4-15 


Means 


64-8 


13-0 


7° '9 


i4'3 


847 


18-1 


ioi'o 


20*6 


98-2 


28-1 


106-1 


29 '9 



MEAN SCOTTISH METEOROLOGY. 



245 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVIL, XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1874. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


126-1 


35-5 


96-7 


34-0 


93-0 


33-4 


_ 


_ 


_ 


_ 


55-2 


13-3 


Kirkwall 








- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Stornoway 








106-0 


30-0 


106-0 


31-0 


88-0 


25-0 


75-0 


22 


- 


- 


49-0 


11-0 


Culloden 








128-0 


37 3 


127-0 


31-8 


116-3 


29-9 


_ 


_ 


_ 


._ 


57-9 


6-6 


Braemar . 








129-0 


30-0 


126-3 


29-0 


111-8 


28-0 


110-0 


18-2 


90-0 


12-3 


76-8 


5-0 


Aberdeen 








- 


36-5 


- 


32-4 


- 


30-5 


- 


24-4 


- 


24-6 


- 


10-8 


Nookton 








114-5 


38-2 


110-5 


31-2 


102-5 


27-2 


89-5 


21-2 


67 5 


15-2 


48-5 


3-2 


Cardross 








- 


43-0 




- 


- 


- 


- 


- 


- 


_ 


- 


- 


Balloch Castle 








120-0 


39-0 


102-0 


32-0 


85-0 


32-0 


63-0 


25-0 


55-0 


20-0 


45-0 


5-0 


Callton Mor . 








110-0 


40-0 


103-0 


38-0 


90-0 


34-0 


76-0 


26-0 


66-0 


25-0 


55-0 


14-0 


Eallabus 








122-0 


29-5 


117-5 


29-0 


97-0 


31-0 


91-0 


24-0 


67-0 


24-0 


75-0 


12-0 


Paisley . 








99-5 


38-0 


97-0 


34-0 


94-5 


30-5 


84-5 


24-5 


69-5 


19-0 


61-5 


5-0 


Auchendrane . 








125-0 


38-0 


118-0 


36-0 


99-0 


35-0 


93 


24-0 


59-0 


20-0 


49-0 


8-0 


Glasgow 








105-2 


33-3 


93-4 


30-2 


106-4 


23-8 


73-8 


23-2 


66-8 


17-2 


48-0 


5-5 


Douglas Castle 








121-0 


33-0 


125-0 


35-0 


109-0 


31-0 


104-0 


24-0 


89-0 


18-0 


70-0 


5-0 


Smeaton 








121-0 


35-5 


105-0 


31-5 


102-0 


27-5 


88-0 


22-0 


78-0 


14-5 


59-0 


1-5 


Thurston 








1100 


42-0 


108-0 


40-0 


96 


35-0 


96-0 


30-0 


86-0 


25-0 


58-0 


13-0 


Thirlestane Castle 








- 


32-0 


- 


28-0 


- 


27-0 


_ 


24-0 


_ 


15-0 


- 


-6-0 


South Cairn . 








110-0 


32-0 


95-0 


27-0 


- 


- 


68-0 


23-0 


62-0 


20-0 


- 


- 




1747-3 


642-8 


1630-4 


550-1 


1390-5 


480-8 


111-8 


355 5 


855-8 


269-8 


807-9 


112-9 




+15 


+ 18 


+ 15 


+ 17 


+ 14 


+ 16 


+13 


+ 15 


+ 12 


+ 14 


+ 14 


+16 


Means 


116-5 


357 


1087 


32 '4 


99 '3 


30-0 


8S-S 


237 


7*'3 


19 '3 


577 


7"i 



1875 










July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


_ 


_ 


114-2 


350 


106-2 


28-0 


85-2 


28-3 


61-4 


18-5 


_ 


_ 


Kirkwall 










- 


- 


- 


_ 


- 


_ 


64-5 


_ 


- 


_ 


- 


_ 


Stornoway 










112-0 


29-0 


98-0 


29-0 


98-0 


32-0 


73-0 


25-0 


57-0 


20-0 


52-0 


15-0 


Braemar . 










134-0 


32 


125-8 


31-8 


115-4 


27-0 


92-3 


23-2 


68-8 


3-0 


69-0 


11-8 


Aberdeen 










- 


34-5 


- 


40-5 


- 


31-2 


- 


28-0 


- 


16-7 


_ 


22-1 


Nookton 










116-5 


- 


102-5 


_ 


99-5 


31-2 


82-5 


23-2 


63-5 


16-2 


50-5 


18-2 


Balloch Castle 










110-0 


30-0 


110-0 


33-0 


90-0 


25-0 


60-0 


22-0 


55-0 


10-0 


55-0 


5-0 


Callton Mor . 










108-0 


36-0 


103-0 


35-0 


97-0 


30-0 


76-0 


27-0 


60-0 


16-0 


61-0 


16-0 


Eallabus 










118-0 


30-0 


123-5 


32 


104-0 


33-0 


80-0 


24-0 


68-0 


16-0 


52-0 


12-0 


Paisley . 










103-5 


27-0 


105-5 


29-1 


97-5 


23-0 


82-5 


22-0 


75-5 


22-0 


63-5 


11-0 


Annanhill 










136-4 


38-0 


136-4 


42-0 


126-0 


36-5 


113-0 


28-6 


87-5 


19-0 


69-5 


17 


Glasgow 










106-7 


32 


89-4 


371 


92-0 


31-5 


74-1 


•20-6 


64-8 


9-0 


57-8 


8-9 


Ridge Park . 










101-5 


37-5 


100-0 


38-5 


101-0 


36-0 


75-0 


27-0 


70-5 


17-0 


50-0 


160 


Douglas Castle 










108-0 


30-0 


116-0 


33-0 


126-0 


27-0 


90 


21-0 


87-0 


9-0 


79-0 


9-0 


Smeaton 










110-0 


25-5 


109-0 


31-5 


104-0 


25-5 


97-0 


17-5 


77-0 


12-5 


68-0 


15-5 


Thurston 










110-0 


36-0 


113-0 


44-0 


108-0 


35-0 


95-0 


28-0 


86-0 


22-0 


61-0 


24-0 


Thirlestane Castle 










115-0 


25-0 


122-0 


32-0 


117-0 


26-0 


99-0 


18-0 


98-0 


12-0 


71-0 


7-0 




1589-6 


442-5 


1668-3 


523-5 


3581-6 


477-9 


1339-1 


383-4 


1080-0 


238-9 


859-3 


208-5 




+ 14 


+ 14 


+ 15 


+ 15 


+ 15 


+16 


+ 16 


+ 16 


+ 15 


+ 16 


+ 14 


+ 15 


Means 


«3'5 


31-6 


XII'2 


34 "9 


105-4 


29 '9 


837 


24-0 


72-0 


14-9 


61 *4 


13 '9 



VOL. XXXV. PART 3. 



2 R 



246 



PROFESSOR C. PIAZZI SMYTH ON 



T.uii,e XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1876. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


54 3 


20-5 


_ 


_ 


657 


24-0 


_ 


_ 


84-5 


28-5 


104-3 


34-5 


Kirkwall 










- 


- 


- 


- 




- 


- 


- 


90-6 


- 


108-6 




Stornoway 










- 


18-0 


- 


11-0 


- 


18-0 




15-0 




20-0 


- 


32-0 


Culloden 










88-0 


11-8 


90-0 


13-5 


102-0 


13-9 


123-5 


19-9 


130-0 


19-6 


135-9 


31-6 


Braemar . 










65-2 


9-0 


78-0 


100 


96-8 


11-2 


108-0 


16-3 


119-2 


19-4 


130-0 


27-2 


Aberdeen 










- 


161 


- 


20-2 


- 


18-7 


- 


21-4 


- 


277 


- 


- 


Oclitertyre 










103-0 


14-0 


105-0 


17-0 


111-0 


14-0 


122-0 


140 


109-0 


22-0 


123-0 


30-0 


Dollar . 










72-7 


17-7 


87-7 


21-7 


84-7 


217 


94-7 


21-7 


104-7 


28-7 


116-7 


36-7 


Balloch Castle 










55-0 


11-0 


46 


11-0 


75-0 


12-0 


98-0 


10-0 


100-0 


15-0 


125-0 


25-0 


Callton Mor . 










65-0 


18-0 


66-0 


20-0 


72-0 


20-0 


910 


22-0 


95-0 


27-0 


106-0 


32-0 


Eallabus 










65-0 


15-0 


76-0 


15-0 


- 


- 


- 


- 


- 


- 




- 


Paisley . 










69-5 


19-0 


62-5 


14-0 


65-5 


14-0 


- 


16-0 


- 


18-1 


- 


- 


Annanhill 










61-7 


19-0 


81-4 


20-0 


104-5 


17-5 


124-7 


18-0 


- 


- 


- 


_ 


Glasgow 










54-2 


15-5 


59-0 


14-5 


59-9 


15-2 


76-9 


16 


133-2 


21-2 


133-8 


30-2 


Ridge Park 










53-0 


18-0 


56-0 


20-0 


64-0 


19-0 


81-0 


20-0 


96-0 


23-0 


108-0 


34-5 


Douglas Castle 










78-0 


12-0 


81-0 


10-0 


83-0 


14-0 


87-0 


17-0 


97-0 


20-0 


109-0 


29-0 


Smeaton 










67-0 


10-5 


72 


12-5 


69-0 


16-5 


91-0 


12-5 


92-0 


16-5 


104-0 


26-5 


Thurston 










70-0 


15-0 


81-0 


22-0 


75-0 


23-0 


93-0 


18-0 


98-0 


27-0 


105-0 


38-0 


Thirlestane Castle 










72-0 


5-0 


83-0 


8-0 


90-0 


13-0 


102-0 


- 


104-0 


- 


120-0 


- 




1093-6 


265-1 


1124-6 


260-4 


1218-1 


285-7 


1292-8 


257-8 


1453-2 


333-7 


1629-3 


407-2 




-=-16 


-5-18 


4-15 


-5-17 


4-15 


-5-17 


-5-13 


-5-15 


-=-14 


-5-15 


4-14 


-=-13 


Mkahs 


68- 4 


147 


75 "o 


i5'3 


8l -2 


16 -8 


99"4 


17*2 


103-8 


22 - 2 


116-4 


31 "3 





January. 


February. 


March. 


April. 


May. 


June. 


1877. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 
17-5 


Max. 


Min. 


Sandwick . ... 


46-6 


16-0 


50-1 


19-7 


_ 


_ 


_ 


_ 


79-2 


106-3 


38-4 


Stornoway 








- 


10-0 


- 


14-0 


- 


16-0 


- 


21-0 


- 


22-0 


- 


35-0 


Culloden 








82-8 


11-1 


- 


- 


109-0 


16-6 




- 


123-2 


20-2 


- 


- 


Braemar . 








- 


4-0 


- 


16-0 


- 


12-0 


115-0 


15-0 


119-0 


16-4 


132-3 


29-3 


Aberdeen 








- 


17-4 


- 


19-0 


- 


14-0 


- 


231 


- 


- 


- 


36-7 


Ochtertyre 








77-0 


10 


92-0 


21-0 


95-0 


21-0 


89-0 


21-0 


103-0 


21-0 


129-0 


34-0 


Dollar . 








72-7 


17-7 


82-7 


17-7 


84-7 


19-7 


86-7 


23-7 


88-7 


22-7 


106-7 


34-7 


Balloch Castle 








47-0 


12-0 


52-0 


15-0 


55-0 


15-0 


65-0 


18-0 


- 


- 


- 


- 


Callton Mor . 








57-0 


22-0 


59-0 


20-0 


65-0 


19-0 


80-0 


22-0 


105-0 


21-0 


100-0 


39 


Eallabus 








55-0 


15-0 


65-0 


19-0 


78-0 


16-0 


84-0 


23-0 


97-0 


18-0 


115-0 


31-0 


Paisley . 








62-0 


13-0 


68-5 


13-0 


98-5 


15-0 


77-5 


17-0 


74-5 


16-0 


94-5 


32-0 


Annanhill 








65-0 


20-7 


85-0 


9-5 


102-1 


20 


109-8 


25-0 


122-9 


23-0 


136-4 


39-0 


Ridge Park 








51-0 


16-0 


59-0 


13-5 


74-0 


16-5 


78-0 


210 


82-0 


22-0 


111-0 


36-0 


Douglas Castle 








66-0 


12 


49-0 


14-0 


96-0 


11-0 


87-0 


18-0 


88-0 


17-0 


92-0 


31-0 


Edinburgh 








- 


20-0 


- 


16-5 


91-0 


18-0 


- 


- 


- 


24-5 


- 


- 


Smeaton 








67-0 


11-5 


80-0 


12-5 


78-0 


10-5 


87-0 


15-5 


92-0 


16-5 


100-0 


25-5 


Thurston 








78-0 


20-0 


75-0 


23-0 


82-0 


19-0 


89-0 


26-0 


86-0 


27-0 


105-0 


36-0 


Thirlestane Castle 








79-0 


6-0 


93 


5-0 


104-0 


10-0 


99-0 


15-0 


99-0 


17-0 


1130 


25-0 




906-1 


254-4 


910-3 


268-4 


1212-3 


269-3 


1147-0 


304-3 


1359-5 


321-8 


1441-2 


502-6 




-5-14 


-5-18 


4-13 


4-17 


-5-14 


4-17 


4-13 


4-15 


4-14 


4-16 


4-13 


4-15 


Means 


647 


14-1 


70 'O 


15-8 


86-6 


iS-8 


88-2 


20-3 


97-1 


20'I 


110-9 


33'S 



MEAN SCOTTISH METEOROLOGY. 



247 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1876. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


104-5 


35-6 


93-4 


36-5 


77-2 


33-5 


63-2 


32-5 


_ 


_ 


47-2 


26-1 


Kirkwall 








98-6 


- 


78-6 


- 


91-1 


- 


- 


- 


- 


- 




_ 


Stornoway 








- 


35-0 




36-0 


- 


35-0 


- 


28-0 


- 


24-0 


- 


24-0 


Culloden 








139-8 


37-7 


141-7 


33-8 


130-5 


28-9 


122-4 


24-6 








- 


Braemar 








129-8 


30-3 


127-0 


31-2 


115-1 


27-4 


- 


- 


- 


- 


68-8 


22-0 


Aberdeen 








- 


- 


- 


34-2 


_ 


31-4 


- 


30-1 


- 


22-5 


- 


24-8 


Ochtertyre 








118-0 


36-0 


121-0 


32 


111-0 


27-0 


103-0 


29-0 


100-0 


14-0 


76-0 


21-0 


Dollar . 








110-7 


40-7 


1177 


37-7 


104-7 


34-7 


94-7 


33-7 


91-7 


18-7 


64-7 


23-7 


Balloch Castle 








120-0 


35-0 


115-0 


30-0 


102-0 


25-0 


65-0 


22-0 


65-0 


14-0 


45-0 


16-0 


Callton Mor . 








105-0 


35-0 


107-0 


33-0 


91-0 


29-0 


83-0 


26-0 


68-0 


20-0 


58-0 


25-0 


Ballabus 








120-0 


31-0 


117-0 


32 


104-0 


25-0 


87-0 


27-0 


71-0 


20-0 


57-0 


24-0 


Paisley . 








- 


36-0 


- 


28-0 


- 


26-0 




27-0 


- 


12-0 


61-5 


21-0 


Annanbill 








138-2 


39-0 


136-2 


30-0 


128-0 


33-0 


123-0 


25-0 


94-2 


18-7 


61-2 


25-0 


Glasgow 








133-7 


32-0 


126-8 


31-2 


124-0 


28-6 


113-2 


22-8 


99-3 


13-1 


66-8 


21-6 


Ridge Park 








105-0 


40-0 


119-0 


31-5 


88-0 


32-0 


74-0 


29-5 


59-0 


10-0 


49-5 


24-0 


Douglas Castle 








103-0 


33 


118-0 


28-0 


102-0 


28-0 


85-0 


24-0 


80-0 


11-0 


66-0 


20-0 


Smeaton 








115-0 


26-5 


115-0 


26-5 


103 


28-5 


94-0 


24-5 


72-0 


16-5 


68-0 


20-5 


Thurston 








116-0 


37-0 


117 


38-0 


101-0 


38-0 


101-0 


32-0 


83-0 


25-0 


71-0 


28-0 


Thirlestane Castle 








123-0 




122-0 


- 


103-0 


29-0 


92-0 


21-0 


81-0 


12-0 


79-0 


9-0 




1880-3 


559-8 


1872-4 


549-6 


1675-6 


540-0 


1300-5 


458-7 


964-2 


251-5 


939-7 


375-7 




-=-16 


-=-16 


-=-16 


-=-17 


-=-16 


-=-18 


-=-14 


-=-17 


-=-12 


-M5 


-fl5 


-=-17 


Means 


«7'5 


35 'o 


117-0 


3 2 '3 


1047 


30-0 


92-9 


27-0 


80-4 


16-8 


62-6 


22 T 



1877 








July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


106-1 


40-3 


_ 




907 


32-3 


83-1 


23-5 


63 4 


22-4 


51-2 


15-5 


Stornoway 








- 


37 


- 


370 


- 


30 


- 


25-0 


- 


24-0 


- 


18-0 


Culloden 








- 


- 


_ 


_ 


_ 


_ 


_ 


_ 


- 


- 


- 


- 


Braemar 








136-0 


33-8 


134-0 


25-2 


128-0 


25-4 


114-4 


190 


97-6 


15-3 


84-0 


9-0 


Aberdeen 








_ 


39-2 


_ 


34-2 


_ 


311 


- 


22-8 


- 


21-9 


- 


9-6 


Ochtertyre 








108-0 


37-0 


122-0 


340 


119-0 


29-0 


112-0 


19-0 


95-0 


17-0 


75-0 


120 


Dollar . 








101-7 


34-7 


1077 


30-7 


_ 


_ 


_ 


- 


72-7 


21-7 


617 


16-7 


Balloch Castle 








_ 


_ 


100-0 


32 


93-0 


28-0 


78-0 


24-0 


60-0 


22-0 


52-0 


15-0 


Callton Mor . 








90-0 


39-0 


100-0 


30 


90-0 


27-0 


70-0 


25-0 


65-0 


26-0 


63 


18-0 


Eallabus 








109-0 


30-0 


108-0 


33-4 


105-0 


26-0 


79-0 


23-0 


71-0 


25-0 


60-0 


25-0 


Paisley . 








86-5 


33-0 


89-5 


29-0 


90-0 


21-0 


86-5 


24-0 


71-5 


20-0 


61-5 


14-0 


Annanhill 








133-0 


39-0 


_ 


_ 


_ 


_ 


100-3 


25-1 


77-1 


27-1 


60-0 


20 


Ridge Park . 








77-5 


37-0 


90 


36-0 


86-0 


30-0 


85-0 


25-0 


63-5 


24 


49-5 


20-0 


Douglas Castle 








85-0 


33 


92 


32-0 


103-0 


25-0 


103-0 


23-0 


86-0 


22-0 


58-0 


15-0 


Edinburgh 








- 


_ 


_ 


30-9 


116-5 


27-0 


94-5 


18-0 


81-0 


17-0 


63 


17-4 


Smeaton 








98-0 


30-5 


96-0 


26-5 


90-0 


23-5 


87-0 


16-5 


76-0 


13-5 


64-0 


15-5 


Thurston 








94-0 


41-0 


99-0 


37-0 


100-0 


35-0 


89-0 


27-0 


81-0 


24-0 


66-0 


18-0 


Thirlestane Castle 








109-0 


29-0 


112-0 


29-0 


112-0 


27-0 


103-0 


17-0 


97-0 


16-0 


70-0 


14-0 




1333-8 


533-5 


1250-2 


476-9 


1323-2 


417-3 


1284-8 


356-9 


1157-8 


358-9 


938-9 


272-7 




-=-13 


-H5 


-=-12 


-fl5 


-=-13 


-=-15 


-rl4 


-i-16 


-fl5 


-fl7 


-fl5 


-M7 


Means 


102 -6 


35 '6 


104-2 


31-8 


101 "8 


27-8 


91-8 


22-3 


77 '2 


21 - i 


62-6 


16 - o 



248 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 



1878 










January. 


February. 


March. 


April. 


May. 


June. 




Max. 


Min. 


Mas. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


53-4 


23-5 


64-2 


22-4 


66-2 


15-5 


85-1 


23-5 


_ 


_ 


112-2 


27-4 


Stomoway 










61-0 


18 


- 


27-0 


- 


18-0 


- 


22-0 


- 


28-0 


- 


27-0 


Braemar 










75-8 


11-0 


108-0 


19-7 


106-0 


1-7 


129-3 


13-0 


132-0 


19-8 


141-0 


27-7 


Perth . 










- 




84-0 


26-0 


89-0 


20-0 


97-0 


25-0 


104-0 


31-0 


120-0 


34-0 


Ochtertyre 










89-0 


15-0 


95-0 


23-0 


101-0 


17-0 


103-0 


20-0 


1110 


28-0 


115-0 


29-0 


Dollar . 










777 


177 


66-7 


24-7 


88-7 


16-7 


- 


- 


- 


- 


108-7 


32-7 


Balloch Castle 










54-0 


15-0 


57-0 


27-0 


- 




- 


- 


- 


- 


- 


_ 


Callton Mor . 










58-0 


20-0 


65-0 


29-0 


80-0 


18-0 


96-0 


24-0 


95 


33 


102-0 


32-0 


Eallabus 










62 


21-0 


72-0 


23-0 


73 


17-0 


95-0 


20-0 


113-0 


27-0 


116-0 


27-0 


Paisley . 










64-5 


110 


55-5 


19-0 


83-5 


11-0 


86-5 


15-0 


93-5 


23-0 


98-5 


24-0 


Annanhill 










64-7 


17-4 


77-5 


26-0 


115-2 


20-0 


- 


- 


- 


- 


140-9 


31-0 


Ridge Park 










53-5 


17-5 


68-0 


23-0 


69-0 


20-5 


87-0 


25-0 


91-5 


29-5 


107-0 


28-0 


Douglas Castle 










80-0 


14-0 


80-0 


17-0 


87-0 


130 


94-0 


17-0 


92-0 


23-0 


109-0 


22-0 


Edinburgh 










73-8 


10-0 


86-0 


19-0 


97-4 


12-9 


108-8 


16-5 


120-0 


26-0 


- 


_ 


Smeaton 










70-0 


12-5 


79-0 


16-5 


89-0 


14-5 


91-0 


18-5 


100-0 


18-5 


113-5 


19-5 


Thurston 










77-0 


19-0 


74-0 


27-0 


79-0 


23-0 


85-0 


24-0 


94-0 


33-0 


105-0 


34-0 


Thirlestane Castle 










77-0 


7-0 


92-0 


12-0 


! 92-0 


13-0 


102-0 


18-0 


106-0 


25-0 


116-0 


26-0 




1091-4 


249-6 


1223-9 


381-3 


1316-0 


251-8 


1259-7 


281-5 


1252-0 


344-8 


1604-8 


421-3 




-=-16 


-=-16 


-fl6 


-=-17 


-=-15 


-=-16 


-=-13 


vl4 


4-12 


-=-13 


-=-14 


-=-15 


Means 


68-2 


i5'6 


76-5 


22-4 


877 


iS7 


96-9 


2Q-I 


i°4 "3 


26-5 


114-6 


28-1 




MEAN SCOTTISH METEOROLOGY. 



249 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES 1 . 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII. r XXVIII. 





July. 


August. 


September. 


October. 


November. 


December. 


1878. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


103-0 


41-7 


108-2 


32-3 


105-0 


38-0 


76-2 


27-5 


57-4 


18-3 


50-2 


13-7 


Stornoway 










- 


- 


- 


36-0 


- 


34-0 


- 


25-0 


- 


- 


_ 


_ 


Braemar . 










147-5 


31-0 


141-0 


29-7 


126-0 


29-4 


116-7 


22-0 


90-0 


14-8 


84-3 


1-0 


Perth . 










127-0 


36-0 


124-0 


35-0 


113-0 


34-0 


98-0 


26-0 


85-0 


17-0 


63-0 


5-0 


Ochtertyre 










123-0 


34-0 


119-0 


36-0 


115-0 


32-0 


107-0 


23-0 


88-0 


20-0 


79-0 


11-0 


Dollar . 










109-7 


29-7 


108-7 


39-7 


1057 


33-7 


97-7 


28-7 


86-7 


21-7 


72-7 


9-7 


Balloch Castle 










115-0 


37-0 


- 


- 


100-0 


30-0 


75-0 


26-0 


58-0 


17-0 


40-0 


8-0 


Callton Mor . 










111-0 


36-0 


108-0 


34-0 


96-0 


38-0 


82-0 


29-0 


63-0 


_ 


61-0 


11-0 


Ballabus 










115-0 


33-0 


104-0 


34-0 


97-0 


33-0 


78-0 


24-0 


59-0 


18-0 


57-0 


8-0 


Paisley . 










102-5 


36-0 


104-5 


340 


100-5 


31-0 


93-5 


19-0 


84-5 


16-0 


69-5 


2-0 


Annanhill 










136-7 


40-0 


135-9 


42-6 


125-2 


32-5 


107-0 


26-0 


76-4 


21-3 


- 


_ 


Ridge Park 










117-0 


40-0 


116-0 


40-0 


90-0 


36-0 


73-0 


27-5 


56-0 


17-0, 


46-0 


2-0 


Douglas Castle 










106-0 


32-0 


111-0 


31-0 


112-0 


27-0 


96-0 


19-0 


75-0 


14-0 


60-0 


2-0 


Edinburgh 










- 


- 


125-0 


33-3 


- 


- 


103-0 


25-0 


72-5 


19-5 


- 


- 


Srneaton 










114-0 


26 5 


1110 


30-5 


105-0 


20-5 


93-0 


17-5 


67-0 


15-5 


62-0 


0-6 


Thurston 










108-0 


40-0 


107-0 


41-0 


102-0 


38-0 


95-0 


31-0 


79-0 


25-0 


73-0 


10-0 


Thirlestane Castle 










123-0 


31-0 


1120 


35-0 


123-0 


25-0 


108-0 


21-0 


91-0 


15-0 


77-0 


3-0 




1758-4 


523-9 


1735-3 


564-1 


1615-4 


512-1 


1499-1 


417-2 


1188-5 


270-1 


894-7 


87.0 




-M5 


-M5 


-7- 15 


-7- 16 


-7- 15 


■t-16 


-rl6 


-7-17 


-t-16 


-=-15 


-7-14 


-fl4 


Means 


1 17 '2 


34"9 


«5'7 


35 '3 


1077 


32-0 


93 '7 


24'5 


74 '3 


18 -o 


63 '9 


6-2 







































July. 


August. 


September. 


October. 


November. 


December. 


1879. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


97-2 


36-5 


110-2 


39-5 


115-1 


35-5 


78-2 


26-5 


79-2 


23-3 


577 


11-5 


Culloden 










131-0 


37-0 


134-3 


33-0 


124-3 


27-8 


117-0 


20-0 


94-0 


17-8 


61-8 


6-8 


Braemar . 










137-5 


30-0 


130-2 


29-0 


120-2 


23-3 


118-8 


16-3 


99-2 


12-7 


70-0 


- 3-0 


Perth . 










120-0 


38-0 


115-0 


40-0 


- 


_ 


- 


- 


- 


- 


58-0 


7-0 


Ochtertyre 










118-0 


37-0 


114-0 


32-0 


105-0 


25-0 


109-0 


21-0 


100-0 


15-0 


74-0 


8-0 


Dollar . 










103-7 


35-7 


103-7 


34-7 


- 


- 


- 


- 


- 


- 


- 


- 


Balloch Castle 










- 


- 


- 


- 


_ 


_ 


- 


- 


65-0 


15-0 


50-0 


8-0 


Callton Mor . 










95-0 


38-0 


93-0 


31-0 


91-4 


32-6 


74-4 


26-5 


70-4 


20-5 


51-4 


10-5 


Eallabus 










98-0 


34-0 


95-0 


30-0 


89-0 


28-0 


81-0 


22-0 


65-0 


19-0 


50-0 


8-0 


Paisley . 










93-5 


36-0 


87-5 


30-0 


93-5 


25-0 


_ 


- 


- 


- 


69-5 


5-0 


Annanhill 










_ 


- 


131-1 


35-9 


119-1 


32-5 


109-4 


20-4 


77-3 


17-1 


62-0 


5-0 


Bidge Park 










96-0 


41-5 


99-0 


36-0 


85-0 


29-0 


85-0 


20-0 


64-0 


18-0 


51-0 


o-o 


Douglas Castle 










96-0 


35-0 


101-5 


28-5 


110-5 


22-5 


114-5 


14-5 


89-5 


10-5 


81-5 


- 6-0 


Edinburgh 










123-7 


30-7 


127-0 


33-8 


- 


_ 


82-7 


18-7 


75-5 


13-5 


52-0 


- 2-0 


Smeaton 










107-0 


31-5 


107-0 


28-5 


96-0 


20-5 


92-0 


14-5 


78-0 


10-5 


67-0 


- 4-5 


Thurston 










98-0 


40-0 


105-0 


42-0 


100-0 


32-0 


100-0 


28-0 


- 


- 


- 


- 


Thirlestane Castle 










129-0 


32-0 


127-0 


32-0 


125-0 


24-0 


125-0 


20-0 


112-0 


14-0 


- 


-11-0 




1643-6 


532-9 


1780-5 


535-9 


1374-1 


357-7 


1287-0 


268-4 


1069-1 


206-9 


855-9 


+ 43-3 




-7-15 


-7-15 


-r-16 


-7-I6 


-f-13 


-fl3 


-f-13 


-7-13 


-f-13 


H-13 


-7-14 


-7-15 


Means 


109-6 


35 '5 


111-3 


33 '5 


i°57 


27 - 5 


99-0 


20 '6 


82-2 


i5'9 


61 -i 


2-9 



VOL. XXXV. PART 3. 



2 s 



250 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


Febr 


nary. 


March. 


April. 


May. 


June. 


1880. 
























Max. 


Mln. 


Max. 


Mln. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


56-2 


25-1 


60-3 


25-3 


70-2 


25-5 


80-1 


29-1 


98-0 


31-6 


109-7 


30-5 


Oulloden 








90-2 


15-0 


101-0 


18-0 


113-0 


18-5 


125-0 


22-0 


130-8 


24-0 


132-0 


28-0 


Braemar . 








87-2 


9-6 


98-8 


13-3 


115-3 


11-0 


119-0 


18-0 


137-0 


19-5 


146-8 


26-0 


Perth . 








72-0 


12-0 


79-0 


25-0 


98-0 


20-0 


101-0 


25-0 


114-0 


26-0 


120-0 


34-0 


Ochtertyre 








81-0 


14-0 


- 


19-0 


110-0 


19-0 


113-0 


22-0 


125-0 


22-0 


120-0 


27-0 


Dollar . 








62-7 


15-7 


74-7 


23-7 


91-7 


22-7 


86-7 


24-7 


109-7 


27-7 


100-7 


31-7 


Balloch Castle 








55-0 


10-0 


60-0 


24 


70-0 


19-0 


88-0 


20-0 


105-0 


24-0 


110-0 


28-0 


CalltonMor . 








51-4 


18-5 


71-4 


26-5 


75-4 


25-5 


85-4 


24-5 


92-4 


26-5 


100-4 


30-5 


Eallabus 








54-0 


14-0 


60-0 


22-0 


70-0 


" 23-0 


90-0 


22-0 


104-0 


24-0 


115-0 


25-0 


Paisley . 








62-5 


11-0 


69-5 


21-0 


73-5 


16-0 


88-5 


19-0 


96-5 


20-0 


103-5 


24-0 


Aimanhill 








68-7 


18-0 


85-8 


26-0 


113-4 


22-1 


122-2 


25-0 


- 


_ 


_ 


_ 


Kidge Park . 








52-0 


11-0 


66-0 


28-0 


86-0 


21-0 


87-0 


25-0 


89-0 


25-0 


103-0 


31-0 


Douglas . 








81-5 


6-5 


90-5 


18-5 


112-5 


9-5 


97-5 


15-5 


91-5 


18-5 


98-5 


21-5 


Edinburgh 








64-0 


12-0 


81-7 


17-5 


77-0 


17-6 


91-5 


22-0 


104-5 


26-4 


_ 


_ 


Smeaton 








79-0 


5-5 


76-0 


15-5 


85-0 


10-5 


93-0 


12-5 


100-0 


12-5 


108-0 


17-5 


Thii'lestane Castle 








69-0 


3-0 


69-0 


22-0 


95-0 


17-0 


101-0 


16-0 


- 


15-0 


118-0 


19-0 




1086-4 


200-9 


1143-7 


345-3 


1456-0 


297-9 


1568-9 


3423 


1497-4 


342-7 


1585-6 


373-7 




-j-16 


-=-16 


■fl5 


-=-16 


-=-16 


-=-16 


-=-16 


-=-16 


-=-14 


-=-15 


-fl4 


H-14 


MEAN8 


67-9 


12 "6 


76-2 


21'6 


91-0 


18-6 


98-1 


21-4 


107-0 


22'8 


JI 3"3 


267 





January. 


February. 


March. 


April. 


May. 


June. 


1881. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


53-2 


- 2-3 


57-7 


18-5 


66-2 


2-5 


75-4 


24-5 


104-3 


25-4 


115-0 


27-9 


Inverness 










- 


- 


92-0 


17-5 


108-0 


18-0 


111-2 


19-0 


118-0 


28-5 


122-0 


31-0 


Braemar . 










86-0 


- 3-0 


93-8 


2-7 


108 3 


o-o 


117-0 


9-0 


134-2 


21-2 


138-0 


17-3 


Ochtertyre 










84-0 


o-o 


103-0 


9-0 


110-0 


16-0 


114-0 


18-0 


125-0 


24-0 


132 


24-0 


Dollar . 










66-7 


2-7 


79-7 


12-7 


86-7 


8-7 


897 


20-7 


1067 


27-7 


106-7 


30-7 


Balloch Castle 










- 


- 


- 


- 


- 


- 


95-0 


15-0 


122-0 


24-0 


127-0 


23-0 


Callton Mor . 










56-4 


5-5 


66-4 


19-0 


73-4 


13-5 


82-4 


19-5 


99-4 


25-5 


104-4 


25-5 


Eallabus 










54-0 


2-0 


62-0 


15-0 


75-0 


12-0 


- 


17-0 


- 


25-0 


- 


25-0 


Paisley . 










61-5 


- 7-0 


78-5 


150 


86-5 


10-0 


91-5 


16-0 


109-5 


25 


109-5 


23-0 


Ridge Park 










48-0 


- 6-0 


61-0 


16-0 


80-0 


11-0 


81-0 


19-5 


115-0 


29-0 


112-5 


30-5 


Douglas Castle 










75-5 


0-5 


85-5 


11-5 


105-5 


6-5 


88-5 


13-5 


110-5 


21-5 


112-5 


24-5 


Edinburgh 










80-8 


2-8 


80-0 


14-8 


98-7 


8-7 


114-0 


177 


127-4 


26-5 


123-7 


30-0 


Smeaton 










75-0 


- 5-5 


_ 


_ 


91-0 


4-5 


90-0 


14-5 


116-0 


24-5 


105-0 


24-5 


Thirlestane Castle 










85-0 


-15-0 


94-0 


4-0 


105-0 


1-0 


108-0 


6-0 


126-0 


15-0 


126-0 


16 




826 1 


-25-3 


953-6 


155-7 


1194-3 


112-4 


1257-7 


229-9 


1514-0 


342-8 


1534-3 


352-9 




-=-12 


-7-12 


-=-12 


■7-12 


-=-13 


-=-13 


-fl3 


-=-14 


-=-13 


-=-14 


-=-13 


-=-14 


Means 


68-8 


- 2'I 


79"S 


13-0 


91-9 


8-6 


967 


16 -4 


116-5 


24"S 


118-0 


25-2 





January. 


Febr 


nary. 


March. 


April. 


May. 


June. 


1882. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


57-2 


27-0 


67-2 


22-5 


69-1 


26-5 


_ 


_ 


1057 


27-8 


105 4 


30-5 


Inverness 








82-0 


24-0 


94-0 


23-0 


105-0 


27-0 


115-0 


25-0 


119-0 


28-0 


120-0 


35-0 


Braemar 








84-0 


12-0 


103-2 


14-0 


112-5 


21-0 


126-7 


11-0 


138-5 


15-6 


140-2 


20-4 


Ochtertyre 








87-0 


21-0 


102-0 


26-0 


109-0 


26-0 


111-0 


21-0 


118-0 


28-0 


116-0 


27-0 


Dollar . 








627 


21-7 


80-7 


24-7 


88-7 


13-7 


89-7 


15-7 


98-0 


26-0 


102-7 


29-7 


Balloch Castle 








52-0 


12-0 


71-0 


14-0 


76-0 


17-0 


85-0 


16-0 


107-0 


21-0 


116-0 


26-0 


Callton Mor . 








58-4 


24-5 


66-4 


27-5 


81-4 


26-5 


90-4 


20-5 


98-4 


28-5 


106-4 


32-5 


Eallabus 








55-0 


26-0 


58-0 


27-0 


67-0 


28-0 


77-0 


20-0 


110-0 


25-0 


106-0 


33-0 


Paisley . 








64-5 


23-0 


79-5 


29-0 


79-5 


23-0 


93-5 


20-0 


105-5 


27-5 


110-5 


31-0 


Ridge Park . 








54-5 


25-0 


67-0 


26-0 


73-5 


26-0 


91-0 


21-5 


107-0 


26-0 


109-0 


28-5 


Douglas Castle 








_ 


_ 


79-5 


24-5 


90-5 


23 


96-6 


15-5 


104-5 


23 


100-5 


29-5 


Edinburgh 








78-0 


22-5 


82-0 


23-8 


88-0 


25-3 


100-0 


20-0 


127-0 


28-0 


- 


- 


Smeaton 








75-0 


18-5 


88-0 


22-5 


92-0 


25-5 


95-0 


18-5 


104-0 


25-5 


105-0 


28-5 


Marchmont 








57-0 


20-0 


69-0 


20-0 


- 


- 


94-0 


18-0 


113-0 


21-0 


120-0 


29-0 




867-3 


277-2 


1107-5 


324-5 


1132-2 


308-5 


1264-8 


242-7 


1555-6 


350-9 


14577 


386-6 




-=-13 


-=-13 


-=-14 


-=-14 


-=-13 


-=-13 


-=-13 


-=-13 


-=-14 


-=-14 


-=-13 


-f-13 


Means 


667 


21-3 


79-1 


23-2 


8 7 -x 


237 


97 '3 


187 


111*1 


25-1 


II2-I 


297 



MEAN SCOTTISH METEOROLOGY. 



251 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





July. 


August. 


September. 


October. 


November. 


Dece 


nber. 


1880. 


























Mas. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


107-4 


33-5 


106-3 


42-4 


97-3 


32-5 


74-2 


21-7 


57-2 


19-5 


51-6 


12-0 


Culloden 








135-8 


36-0 


136-0 


38 8 


131-8 


29-5 


112-0 


18-0 


92-0 


3-0 


69-1 


7-0 


Braemar . 








138-0 


34 


136-0 


31-0 


130-3 


28-2 


114-8 


9-2 


88-5 


1-6 


71-2 


-0-5 


Perth . 








- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Ochtertyre 








126-0 


35-0 


126-0 


33-0 


123-0 


30-0 


110-0 


15-0 


103-0 


11-0 


93-0 


8-0 


Dollar . 








102-7 


34-7 


109-7 


32-7 


- 


- 


94-7 


10-7 


- 


- 


64-7 


3-7 


Balloch Castle 








- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


Callton Mor . 








97-4 


38-5 


104-4 


36-5 


94-4 


33-5 


77-4 


13-5 


56-4 


12-5 


54-4 


15-5 


Eallabus 








114-0 


33-0 


118-0 


32-0 


99-0 


29-0 


94-0 


16-0 


66-0 


11-0 


58-0 


13-0 


Paisley . 








107-0 


31-0 


109-5 


31-0 


99-5 


- 


87-5 


- 


- 


- 


71-5 


7-0 


Annanhill 








131-7 


38-6 


_ 


_ 


131-7 


31-0 


113-2 


15-8 


69-9 


9-0 


71-2 


14-8 


Ridge Park 








105-0 


38-0 


112-0 


38-0 


98-5 


33-0 


79-5 


16-0 


60-5 


1-0 


53-0 


10 


Douglas Castle 








110-0 


28-5 


114-5 


32-5 


112-5 


24-5 


105-5 


5-5 


86-5 


o-o 


52-5 


12-5 


Edinburgh 








110-0 


36-0 


115-0 


38-5 


- 


- 


75-5 


17-0 


75-5 


13-0 


57-0 


15-0 


Smeaton 








116-0 


26-5 


110-0 


26 


lllti 


15-5 


88-0 


- 


79-0 


10-5 


68-0 


15-5 


Thirlestane Castle 








117-0 


30-0 


133-0 


31-0 


123-0 


25-0 


97-0 


9 


82-0 


-6-0 


84-0 


-1-0 




1618-0 


473-3 


1530-4 


413-4 


1352-0 


311-7 


1323 3 


167-4 


916-5 


86-1 


919-2 


132-5 




4-14 


4-14 


4-13 


4-13 


4-12 


-=-11 


4-14 


-rl2 


4-12 


4-12 


4-14 


4-14 


Means 


115-6 


33'8 


1177 


34'i 


1 12 7 


28-3 


94'5 


14-0 


76-4 


7-2 


657 


9'S 





July. 


Auf 


ust. 


September. 


October. 


November. 


December. 


1881. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


109-2 


37-4 


108-1 


32-3 


94-1 


33-0 


73-7 


31-5 


61-2 


31-7 


53-4 


21-6 


Inverness 










122-0 


43-0 


122-5 


32-0 


125-0 


38-0 


107-0 


28-5 


88-0 


27-0 


80-5 


20-0 


Braemar . 










138-0 


29-0 


132-4 


23-3 


125-0 


25 -2 


114-2 


17-1 


88-0 


14-0 


- 


- 


Ochtertyre 










117-0 


30-0 


119-0 


28-0 


121-0 


28-0 


105-0 


20-0 


100-0 


23-0 


84-0 


17-0 


Dollar . 










94-7 


34-7 


103-7 


30-7 


102-7 


31-7 


91-7 


20-7 


75-7 


18-7 


60-7 


15-7 


Balloch Castle 










113-0 


25-0 


101-5 


16-0 


101-0 


15-0 


76-0 


6-0 


65-0 


9-0 


51-0 


2-5 


Callton Mor . 










97-4 


37-5 


96-4 


29-5 


91-4 


31-5 


- 


- 


65-4 


23 


57-4 


16-5 


Eallabus . 










89-0 


_ 


94-0 


_ 


90-0 


_ 


75-0 


22-0 


65-0 


26-0 


49-0 


19-0 


Paisley . 










93-5 


29-0 


96-5 


25-0 


101-5 


25-0 


79-5 


15-0 


- 


- 


70-5 


13-0 


Ridge Park 










94-5 


36-5 


99-0 


31-5 


86-0 


30-5 


89-0 


21-0 


70-0 


23-0 


50-0 


17-5 


Douglas Castle 










94-5 


32-5 


105-5 


28-5 


109-5 


27-5 


96-5 


16-5 


82-0 


18-0 


64-5 


15-5 


Edinburgh 










106-0 


35-8 


125-0 


31-8 


113-0 


31-7 


101-0 


21-7 


85-0 


21-7 


60-0 


20-5 


Smeaton 










113-0 


31-5 


108-0 


30-0 


96 


30-5 


90-0 


20-5 


75-0 


18-0 


68-0 


15-5 


Thirlestane Castle 










125-0 


30-0 


123 


23-0 


116-0 


20-0 


125-0 


11-0 


- 


- 


- 


- 




1506-8 


431-9 


1534-6 


361-6 


1472-2 


367 6 


1223-6 


251-5 


920-3 


253-1 


749-0 


194-3 




4-14 


4-13 


4-14 


4-13 


4-14 


4-13 


4-13 


4-13 


4-12 


4-12 


4-12 


4-12 


Means . . . 


107-6 


33' 2 


109-6 


27-8 


105-2 


28-3 


94-1 


19 "3 


767 


21 -i 


62-4 


l6 - 2 



1885 










July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


106-1 


39-4 


110-2 


35-5 


105-3 


32-4 


88-2 


27-3 


67-4 


20-5 


53-4 


12-5 


Inverness 










130-0 


40-0 


125-0 


39-0 


115-0 


32-0 


110-0 


27-0 


89-0 


21-0 


67-0 


10-0 


Braemar 










142-0 


33-0 


137-0 


30-0 


122-0 


22-0 


108-0 


19-2 


86-0 


15-0 


74-0 


-11-0 


Ochtertyre 










123-0 


32-0 


136-0 


31-0 


124 


25-0 


118-0 


18-0 


98-0 


17-0 


81-0 


3-0 


Dollar . 










102-0 


36-0 


105-7 


33-7 


100-0 26-0 


85-0 


- 


79-7 


- 


- 


- 


Balloch Castle 










113-0 


37-0 


115-0 


34-0 


103-0 


26-0 


75-0 


19-0 


62-0 


19-5 


47-5 


10-0 


Callton Mor . 










105-4 


39-5 


103-4 


33-5 


90-4 


30-5 


79-4 


24-5 


54-4 


21-5 


48-4 


14-5 


Eallabus 










99-0 


37-0 


104-0 


37-0 


87-0 


29-0 


83-0 


21-0 


54-0 


20-0 


50-0 


11-0 


Paisley . 










105-5 


37-0 


112-5 


30-0 


102-5 


28-0 


80-5 


19-0 


81-5 


18-0 


56-5 


no 


Ridge Park . 










113-0 


42-0 


112-0 


34-0 


89-0 


31-0 


70-0 


23-5 


56-0 


21-0 


49-0 


- 0-2 


Douglas Castle 










103-5 


39-5 


116-5 


31-0 


105-0 


27-0 


83-5 


19-5 


86-5 


14-5 


50-5 


2-5 


Edinburgh 










110-0 


38-8 


124-0 


30-5 


_ 


- 


- 


- 


- 


- 


- 


- 


Smeaton 










106-0 


35-5 


119-0 


31-5 


105-0 


24-5 


88-0 


21-5 


72-0 


20-5 


64-0 


1-5 


Marchmont 










126-0 


31-0 


121-0 


35-0 


105-0 


24-0 


87-0 


20-0 


63-0 


15-0 


58-0 


- 4-0 




1584-5 


517-7 


1641-3 


465-7 


1353-2 


357-4 


1155-6 


259-5 


949-5 


223-5 


699-3 


60-8 




4-14 


4-14 


4-14 


4-14 


4-13 


4-13 


4-13 


4-12 


4-13 


4-12 


4-12 


4-12 


ilEAXS 


113-2 


37 '0 


117-2 


33 '3 


104-1 


27 - 5 


88-9 


21 - 6 


73'° 


18 -6 


58-3 


5'i 



252 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII. , XXVIII. 





Jam 


imy. 


February. 


March. 


Ap 


•il. 


May. 


June. 


1883. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwiok 


55-2 


22-5 


63-8 


24-5 


751 


18-3 


83-2 


33-3 


100-4 


21-0 


117-4 


28-7 


Inverness 








77-0 


22-0 


88-0 


23 


97-0 


19-0 


107-0 


21-0 


116-0 


29-0 


128-0 


33 


Braemar 








81-2 


8-2 


99-0 


19-0 


115-2 


1-0 


119-7 


16-0 


141-0 


21-0 


138-5 


25 


Ochtertyre 








89-0 


21-0 


- 


- 


108-0 


18-0 


- 


- 


- 


- 


125-0 


31-0 


Dollar . 








- 


- 


- 


- 


877 


25-0 


86-7 


29-0 


101-7 


30-0 


101-7 


35-0 


Balloch Castle 








54-0 


22 


70-0 


21-0 


70-0 


16-0 


87-5 


17-0 


102-0 


20-5 


113-0 


27-0 


Callton Mor . 








54-4 


24-5 


59-4 


26-5 


73-4 


17-0 


85-4 


23-0 


91-4 


26-5 


99-4 


32-5 


Eallabus 








56-0 


22-0 


56-0 


23-0 


70-0 


16-0 


87-0 


24-0 


95-0 


25-0 


109-0 


33-0 


Paisley . 








66-5 


24-0 


79-5 


26-0 


81-5 


14-0 


99-5 


21-0 


96-5 


22-0 


97-5 


31-0 


Ridge Park . 








50-5 


21-5 


58-0 


23-0 


- 


- 


81-0 


27-0 


96-0 


23-5 


95-5 


31-0 


Douglas Castle 








67-5 


17-0 


81-5 


18-5 


95-5 


9-0 


101-5 


22-5 


85-5 


16-5 


92-5 


26-0 


Edinburgh 








63-0 


190 


79-0 


22-0 


- 


- 


- 


- 


106-0 


20-0 


108-0 


28-0 


Smeaton 








69-0 


15-5 


79-0 


21-5 


79-0 


17-5 


94-0 


22-5 


102-0 


18-5 


102-0 


25-5 


Marchmont 








54-0 


11-0 


69-0 


14-0 


76 


13-0 


92-0 


22-0 


110-0 


22-0 


109-0 


26-0 




837-3 


250-2 


882-2 


262-0 


1028-4 


183-8 


1124-5 


278-3 


1343-5 


295-5 


1536-5 


412-7 




-=-13 


-M3 


-M2 


-M2 


■M2 


•fl2 


-M2 


-M2 


-=-13 


-M3 


4- 14 


M4 


Mkans 


64-4 


19-2 


73 '5 


21-8 


957 


i5'3 


937 


23-2 


103 '3 


22 -7 


109-8 


29 '5 





January. 


Febr 


uary. 


March. 


April. 


May. 


June. 


1884. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


54-4 


25-4 


62-2 


23-8 


78-2 


24-8 


82-4 


22-4 


87-4 


28-1 


110-2 


29-5 


Inverness 








72-0 


22-0 


87-0 


220 


107-0 


24-0 


108-0 


27-0 


116-0 


28-0 


123-0 


37-0 


Kingussie 








90-0 


4-5 


94-0 


17-0 


- 


- 


- 


- 


- 


- 


139-0 


26-0 


Braemar 








68-8 


14-0 


93-0 


15-7 


107-0 


17-0 


117-3 


12-0 


123-0 


16-0 


_ 


_ 


Ochtertyre 








87-0 


17-0 


98-0 


16-0 


98-0 


27-0 


115-0 


26-0 


124-0 


31-0 


- 


_ 


Dollar . 








66-7 


24-0 


79-7 


23-0 


897 


23-0 


87-7 


27-0 


101-7 


30-0 


1037 


37-0 


Balloch Castle 








52-0 


22-0 


65-0 


20-5 


82-0 


23-0 


98-0 


19-0 


110-0 


22-0 


126-0 


28-0 


Callton Mor . 








51-4 


25-5 


64-4 


20-5 


69-4 


26-5 


86-0 


26-0 


98-4 


26-5 


101-4 


33-5 


Eallabus 








54 


26-0 


61-0 


21-0 


69-0 


22-0 


84-0 


24-0 


103-0 


23 


110-0 


28-0 


Paisley . 








65-0 


17-0 


79-5 


23-0 


78-5 


22-5 


92-5 


23-0 


83-5 


29-2 


93-5 


32-0 


Ridge Park 








50-0 


22-5 


56-5 


25-0 


72-0 


22-0 


84-0 


25-0 


105-5 


28-0 


112-0 


32-0 


Douglas Castle 








53-0 


15-5 


80-5 


20-5 


90-5 


22-5 


100-5 


19-5 


107-5 


26-5 


106-5 


29-5 


Edinburgh 








- 


19-0 


- 


17-0 


- 


19-0 




19-0 


- 


26-0 


- 


- 


Smeaton 








59-0 


15-5 


73-0 


14-5 


88-0 


18-5 


90-0 


15-5 


106-0 


20-5 


105-0 


28-5 


Marchmont 








55-0 


15-0 


64-0 


11-0 


87-0 


12-0 


98-0 


11-0 


109-0 


21-0 


120-0 


26-0 




878-3 


284-9 


1057-8 


290-5 


1116-3 


303 -S 


1243-4 


296-4 


1375-0 


355-8 


1350-3 


367-0 




4-14 


4-15 


M4 


4-15 


4-13 


-=-14 


4-13 


H-14 


-=-13 


4-14 


4-12 


-=-12 


Means 


62-7 


19-0 


75 '6 


19-4 


8S-9 


21 '7 


95 '6 


21 "2 


105-8 


25 "4 


112-5 


30-6 

1 





January. 


Febi 


uary. 


March. 


Ap 


ill. 


May. 


June. 


1885. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


56-2 


21-0 


65-7 


8-3 


73-7 


23-4 


102-2 


19-1 


93-2 


22-4 


100-4 


25-9 


Inverness 










55-0 


15-0 


88-0 


14-0 


98-0 


23-0 


112-0 


25-0 


117-0 


29-0 


118-0 


33-0 


Kingussie 










- 


- 


98-5 


5-5 


105-0 


12-0 


- 


- 


- 


- 


- 


- 


Braemar 










77-0 


3-0 


86-2 


7-0 


102-4 


13-8 


115-8 


16-4 


111-2 


21-4 


132-0 


27-4 


Ochtertyre 










77-0 


18-0 


95-0 


18-0 


108-0 


20-0 


115-0 


24-0 


115-0 


26-0 


121-0 


32-0 


Dollar . 










57-7 


22-0 


77-7 


21-0 


87-7 


20-0 


84-7 


21-0 


91-7 


28-0 


105-7 


33-0 


Callton Mor . 










50-4 


17-5 


61-4 


17-5 


79-4 


19-5 


80-4 


24-5 


87-4 


26-5 


97-4 


29-5 


Eallabne 










57-0 


14-0 


55-0 


16-0 


70-0 


17-3 


78-0 


18-0 


95 


20-9 


104-0 


27-5 


Paisley . 










49-5 


16-9 


57-0 


19-9 


62-3 


18-7 


68-0 


24-2 


71-9 


24-8 


93-3 


30-3 


Douglas Castle 










53-5 


13-5 


75-5 


4-5 


88-5 


13-5 


97-5 


20-5 


82-5 


19-5 


100-5 


26-5 


Edinburgh 










- 


17-0 


- 


15-0 


- 


18-0 


- 


22-0 


- 


22-0 


- 


28-0 


Smeaton 










58-0 


8-5 


78-0 


- 


88-0 


- 


101-0 


20-5 


95-0 


19-5 


115-0 


26-5 


Marchmont . 










51-0 


8-0 


();-.•( 1 


8-0 


82-0 


12-0 


98-0 


15-0 


105-0 


20-0 


129-0 


25-0 




642-3 


174-4 


903-0 


154-7 


1045-0 


211-2 


1052-6 


250-2 


1064-9 


280-0 


1216-3 


344-6 




-Ml 


■fie 


■fl2 


4-12 


-=-12 


M2 


-Ml 


M2 


-Ml 


4-12 


4-11 


•M2 


Means 


58-4 


i4'5 


75 '2 


I2'9 


87-1 


17-6 


957 


20 -8 


96-8 


23 '3 


no'6 


287 



MEAN SCOTTISH METEOROLOGY. 



253 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





\ July. 


August. 


September. 


October. 


November. 


December. 


1883. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


111-3 


33 9 


_ 


_ 


97-2 


31-5 


76-2 


31-5 


65-1 


21-5 


571 


26-5 


Inverness 






126-0 


36-0 


127-0 


40-0 


114-0 


31-0 


108-0 


28-0 


93-0 


23-0 


72-0 


27-0 


Braemar 






142-3 


27-3 


140-0 


30-0 


121-2 


24-0 


108-0 


20-0 


86-0 


13-0 


65-3 


10-0 


Ochtertyre 






- 


- 


- 


- 


120-0 


29-0 


125-0 


24-0 


102-0 


19-0 


85-0 


19-0 


Dollar . 






105-7 


40-0 


104-7 


38-0 


1097 


36-0 


107-7 


26-0 


94-7 


22-0 


66-7 


25-0 


Balloch Castle 






116-0 


310 


109-0 


37-0 


101-0 


27-0 


- 


- 


- 


- 


- 


- 


Callton Mor . 






93-4 


36-5 


99-4 


40-5 


95-4 


30-5 


87-4 


26-5 


64-4 


21-5 


50-4 


20-5 


Ballabus 






117-0 


31-0 


103-0 


34-0 


97-0 


27-0 


82-0 


24-0 


62-0 


19-0 


51-0 


19-0 


Paisley . 






104-5 


35-0 


99-5 


36-0 


104-5 


29-0 


95-0 


21-0 


83-5 


13-5 


66-0 


18-0 


Ridge Park 






101-0 


35-0 


97-5 


38-0 


86-0 


30-0 


71-0 


27-0 


61-0 


20-0 


50-0 


19-0 


Douglas Castle 






98-5 


30-5 


109-5 


35-5 


110-5 


27-5 


99-5 


21-5 


88-5 


13-0 


- 


- 


Edinburgh 






112-0 


35-0 


102-0 


38-0 


- ' 




- 


- 


- 


- 


- 


- 


Smeaton 






108-0 


33-5 


110-0 


34-5 


100-0 


28-0 


95-0 


20-5 


73-0 


16-5 


55-0 


21-5 


Marchmont 






125-0 


31-0 


122-0 


33-0 


100-0 


29-0 


90-0 


23-0 


60-0 


17-0 


57-0 


20-0 




1460-7 


435-7 


1323-6 


434-5 


1356-5 


379-5 


1144-8 


293-0 


933-2 


219-0 


675-5 


225-5 




4-13 


4-13 


4-12 


412 


4-13 


4-13 


4-12 


-=-12 


4-12 


4-12 


411 


4-11 


Means 


112-4 


33 'S 


110-3 


36-2 


i°4 '3 


29-2 


95 '4 


24-4 


77-8 


18-2 


61 "4 


20-5 





July. 


August. 


September. 


October. 


November. 


December. 


1884. 


























Max. 


Min. 


Matx. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


105-2 


28-9 


108-2 


37-5 


99-2 


33-3 


_ 


_ 


_ 


_ 


47-3 


21-0 


Inverness 








- 


- 


120-0 


36-0 


112-0 


35-0 


96-0 


29-0 


66-0 


19-0 


54-0 


19-0 


Kingussie 








- 


_ 


134-5 


30-5 


122-0 


25-5 


107-0 


20-0 


83-5 


8-0 


63-5 


10-0 


Braemar 








126-7 


33-0 


122-2 


31-0 


134-0 


27-0 


117-0 


20-0 


81-0 


9-8 


627 


11-0 


Ochtertyre 








118-0 


37-0 


125-0 


38-0 


115-0 


32 


112-0 


21-0 


89-0 


15-0 


73-0 


17-0 


Dollar . 








107-7 


36-0 


111-7 


32-0 


117-7 


29-0 


103-0 


26-0 


76-7 


15-0 


62-7 


18-0 


Balloch Castle 








1160 


30-5 


115-0 


32-0 


107-0 


28-0 


90 


23-0 


- 


- 


- 


- 


Callton Mor . 








97-4 


35-5 


95-4 


35-5 


85-4 


34-5 


72-4 


30-5 


56-4 


19-5 


57-4 


17-5 


Eallabus 








105-0 


32-0 


90-0 


- 


88-0 


29-0 


74-0 


29-0 


57-0 


18-0 


- 


- 


Paisley . 








86-5 


36-6 


94-8 


37-2 


79-5 


32-9 


71-5 


26-0 


63-0 


19-2 


53-3 


18-0 


Ridge Park 








113-0 


33-0 


110-0 


37-0 


100-0 


33-5 


86-5 


25-5 


58-5 


16-5 


51-0 


15-0 


Douglas Castle 








104-5 


30-5 


111-5 


32-5 


112-5 


30-5 


107-5 


22-5 


76-0 


11-0 


55-5 


12-5 


Edinburgh 








_ 


- 


- 


32-0 


- 


- 


- 


24-0 


- 


15-0 


- 


17-0 


Smeaton 








105-0 


28-5 


110-0 


30-5 


98-0 


26-5 


91-0 


21-5 


71-0 


10-5 


55-0 


9-5 


Marchmont 








119-0 


29-0 


119-0 


28-0 


102-0 


26-0 


90-0 


12-0 


61-0 


11-0 


53-0 


11-0 




1304-0 


390-5 


1567-3 


469-7 


1472-3 


422-7 


1217-9 


330-0 


839-1 


187-5 


688-4 


196-5 




4-12 


4-12 


4-14 


4-14 


414 


4-14 


4-13 


4-14 


4-12 


4-13 


412 


4-13 


Means 


1087 


3 2 '5 


II2'0 


33 "6 


105-2 


30-2 


93 '7 


23-6 


69-9 


14-4 


57'4 


iS'i 





July. 


August. 


September. 


October.. 


November. 


December. 


1885. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Sandwick 


109-7 


27-4 


97-3 


27-5 


90-1 


29-5 


69-1 


20-5 


60-9 


- 


- 


- 


Inverness 








127-0 


41-0 


119-0 


31-0 


114-0 


30-0 


93-0 


20-0 


83-0 


20-0 


74-0 


18-0 


Kingussie 








_ 


_ 


_ 


- 


122-0 


14-5 


103-0 


10-0 


- 


- 


- 


- 


Braemar 








125-2 


31-8 


121-0 


25-5 


122-0 


20-0 


100-0 


9-0 


87-0 


6-4 


83-8 


8-0 


Ochtertyre 








134-0 


35-0 


123-0 


29-0 


115-0 


23-0 


105-0 


19-0 


89-0 


13-0 


95-0 


13-0 


Dollar . 








112-7 


39-0 


108-7 


34-0 


103-7 


27-0 


91-7 


24-0 


76-7 


13-0 


75-0 


14-7 


Callton Mor . 








106-4 


31-5 


106-0 


31-0 


86-0 


23-0 


78-0 


23-0 


57-0 


24-0 


50-0 


11-0 


Eallabus . 








116-0 


32-0 


107-0 


31-0 


87-0 


22-0 


68-0 


17-0 


62-0 


16-0 


52-0 


14-0 


Paisley 








91-3 


37-5 


93-0 


33-2 


76-1 


24-1 


64-2 


19-3 


60-9 


15-5 


54-3 


12-7 


Douglas Castle 








120-5 


30-5 


106-5 


28-5 


108-5 


19-5 


98-5 


16-5 


75-5 


10-5 




- 


Edinburgh 








- 


34-0 


_ 


27-0 


- 


18-0 


- 


15-0 


62-3 


8-5 


54-5 


11-0 


Smeaton . 








114-0 


36-5 


102-0 


32-5 


99-0 


22-5 


81-0 


19-5 


70-0 


12-5 


62-0 


9-5 


Marchmont 








124-0 


26-0 


109-0 


27-0 


102-0 


20-0 


76-0 


23-0 


67-0 


10-0 


59-0 


10-0 




1280-8 


402 2 


1192-5 


357-2 


1225-4 


293-1 


1027-5 


235-8 


851-3 


149-4 


659-6 


121-9 




411 


412 


4-11 


412 


4-12 


4-13 


4-12 


4-13 


4-12 


411 


4 10 


4-10 


Means 


116-4 


33 'S 


108-4 


29-8 


102 -i 


22 -5 


8 5 -6 


18-1 


70-9 


J 3' 6 


66-o 


12 '2 



VOL. XXXV. PART 3. 



2 T 



254 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXVTa. conHmied.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





January. 


February. 


March. 


April. 


May. 


June. 


1886. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Inverness 


_ 


_ 


86-0 


20-0 


102-0 


17-0 


107-0 


24-0 


116-5 


26-5 


115-0 


35 


Kingussie 










98-5 


-14-0 


- 


- 


- 


- 


- 




- 


- 


- 


- 


Braemar . 










88-2 


- 32 


96-2 


2-0 


111-4 


-4-5 


117-0 


14-2 


112-9 


17-3 


123-2 


24-0 


Ochtertyre 










77-0 


4-0 


1007 


11-0 


97-0 


10-0 


1150 


20-0 


112-0 


24-0 


122-0 


32-0 


Dollar 










69-7 


n-o 


79-5 


16-0 


94-0 


19-0 


91-7 


26 


93-0 


31-7 


109-7 


37-0 


Callton Mor 










56-0 


130 


64-0 


11-0 


66-0 


14-0 


86-0 


22-0 


92-0 


27-0 


95-0 


28-0 


Eallabus . 










50-0 


11-0 




14-0 


- 


- 


87-0 


20-5 


88-0 


17-5 


97 


21-0 


Paisley 










50-9 


13-9 


50-9 


10-0 


69-7 


16-0 


72-7 


26-3 


80-9 


29-2 


_ 


_ 


Edinburgh 










51-2 


6 5 


54-9 


- 


77-4 


11-5 


- 


- 


- 


- 


- 


- 


Smeaton . 










59 


7-5 


80-0 


10-5 


83-0 


8-5 


98-0 


22-5 


105-0 


21-5 


111-0 


25-5 


March mont 


- 






52 


o-o 


70-0 


11-0 


90-0 


4-0 


102-0 


18-0 


112-0 


15-0 


116-0 


24-0 




652-5 


49-7 


682-2 


105-5 


790-5 


95-5 


876-4 


193-5 


912-3 


209-7 


888-9 


226-5 




4-10 


4-10 


-=-9 


•=-9 


-=-9 


4-9 


4-9 


4-9 


4-9 


4-9 


4-8 


4-8 


Means 


65-2 


5"o 


75 -8 


117 


87-8 


io - 6 


97 "4 


21-5 


101*4 


2 3 3 


IIZ'I 


28-3 





January. 


February. 


March. 


April. 


May. 


June. 


1887. 
























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Inverness 


81-0 


20-0 


91-0 


27-0 


97-0 


19-0 


107-0 


26-0 


112-0 


29-0 


121-0 


40-0 


Braemar . 










85-0 


9-8 


101-0 


12-0 


120-0 


11-3 


117-0 


17-0 


114-2 


19-3 


137-0 


26-0 


Arbroath 










- 


- 


88-5 


140 


100-5 


16-0 


100-0 


20-0 


97-5 


21-5 


120-0 


27-5 


Ochtertyre 










80-0 


16-0 


99-0 


160 


107-0 


18-0 


111-0 


22-0 


120-0 


27-0 


140 


31-0 


Dollar 










62-7 


21-0 


77-7 


18-0 


87-7 


18-0 


96-7 


25-0 


98-7 


30-0 


108-7 


27-0 


Callton Mor 










55-0 


11-0 


71-0 


25-0 


83-0 


9-2 


89-0 


21-0 


100-0 


27-0 


114-0 


37-0 


Eallabus . 










52-0 


13-0 


60-0 


23-0 


710 


15-0 


77-0 


17-0 


105-0 


18-0 


121-0 


310 


Paisley 










55-9 


19-1 


61-2 


16-0 


62-3 


10-9 


71-6 


21-2 


82-2 


31-1 


104-2 


35 1 


Smeaton . 










67-0 


14-5 


88-0 


11-5 


90-0 


13-5 


94-0 


18-5 


1100 


20-5 


125-0 


26-5 


Marchmont 










69-0 


9-0 


78-0 


8-0 


79-0 


13-0 


94-0 


11-0 


107-0 


18-0 


133-0 


23-0 




607-6 


133-4 


815-4 


170-5 


897-5 


143-9 


957 3 


198-7 


1046 6 


241-4 


1223-9 


304-1 




4-9 


4-9 


4-10 


4-10 


4-10 


4-10 


4-10 


4-10 


4-10 


4-10 


4-10 


4-10 


Means 


67-S 


14-8 


81-5 


17-0 


89-8 


14-4 


95 '7 


19-9 


104-7 


24-1 


122*4 


3°'4 



MEAN SCOTTISH METEOROLOGY. 



255 



Table XXVIa. continued.— BLACK-BULB THERMOMETERS, MAXIMA AND MINIMA EXTREMES. 

A PREPARATORY TABLE FOR THE FROST AND FIRE RETURNS OF TABLES XXVII., XXVIII. 





1886 








July. 


August. 


September. 


October. 


November. 


December. 




Max. 


Mill. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Inverness 

Kingussie 

Braemar 

Ochtertyre 

Dollar 

Callton Mor 

Eallabus . 

Paisley 

Edinburgh 

Smeaton . 

Marchmont 










129-8 
129-0 
1087 
100-0 
103-0 
87-5 

116-0 
122-0 


30-8 
32-0 
37-0 
32-0 
310 
36-5 

31-1 
30-0 


117-0 

127-2 

117-0 

105-7 

97-0 

80-1 
112-0 


38-0 

28-4 
36-0 
37-0 
32-0 

33-0 
28-0 


109-0 

125-8 

117-0 

112-7 

95 -(f 

92-0 

87-1 

107-0 
105-0 


35-0 

24-0 
31-0 
30-0 
29-0 
27-0 
26-4 

25-0 
20-0 


99-0 

111-8 
116-0 

98-7 
88-0 
80-0 
72-6 

93-0 
90-0 


28-5 

20-0 
29-0 
34-0 
28-0 
26-5 
27-8 

26-5 
23-0 


86-0 

91-6 

101-0 
88-0 
70-0 
63-0 
60-6 

73-0 
65-0 


26-0 

21-0 
26-0 
28-0 
28-0 
25-0 
26-8 

21-5 
18-0 


62-0 

76-6 

85-0 
71-7 
50-0 
50-0 
55-8 

50-0 
48-0 


18-0 

-2-0 

11-0 

16-0 

9-0 

8-0 

10-4 

9-0 
3-0 


1 


lEANS 








896-0 
-=-8 

II2'0 


260-4 
4-8 

32-6 


756-0 
4-7 

io8 - o 


232-4 
4-7 

33'2 


950-6 
-=-9 

105-6 


247-4 
4-9 

27'5 


849-1 
4-9 

94"3 


243-3 
4-9 

27-0 


698-2 
4-9 

77 -6 


220-3 
4-9 

24 '5 


549-1 
4-9 

61 -o 


82-4 
4-9 

9-2 





July. 


August. 


September. 


October. 


November. 


December. 


1887. 


























Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Inverness 


124-0 


37 


120-0 


40-0 


114-0 


28-0 


103-0 


25-5 


84-0 


26-0 


73-0 


21-0 


Braemar 










128-2 


29-0 


123-2 


28-2 


118-0 


22-2 


117-0 


192 


93-2 


15-4 


71-3 


5-0 


Arbroath 










110-0 


26-0 


115-0 


30-0 


117-5 


23-0. 


112-0 


19-0 


88-0 


17-0 


77-0 


10-0 


Ochtertyre 










134-0 


32-0 


123-0 


33-0 


118-0 


30-0 


118-0 


25-0 


107-0 


22-0 


r 


- 


Dollar . 










- 


- 


103-7 


35-0 


102-7 


310 


100-0 


28-0 


85-7 


23-0 


69-7 


18-0 


Callton Mor 










107-0 


34-0 


98-0 


31-0 


92-0 


30-0 


92-0 


25-0 


66 


18-0 


49-0 


16-0 


Eallabus 










- 


_ 


_ 


_ 


90-0 


260 


75-0 


22-0 


65-0 


14-0 


51-0 


14 


Paisley . 










91-1 


36-9 


88-0 


35-8 


82-7 


30-9 


81-9 


20-3 


57-1 


18-9 


51-3 


17-1 


Smeaton 










119-0 


27-5 


110-0 


31-5 


107-0 


21-5 


97-0 


17-5 


58-0 


17-5 


52-0 


12-5 


Marchmont 










123-0 


26 


116-0 


27-0 


103-0 


22-0 


91-0 


16-0 


65-0 


15-0 


51-0 


12-0 
125-6 




936-3 


248-4 


996-9 


291-5 


1044-9 


264-6 


986-9 


217-5 


769-0 


186-8 


545-3 




4-8 


4-8 


4-9 


4-9 


4-10 


4-10 


4-10 


4-10 


4-10 


4-10 


4-9 


4-9 


Means 


117*0 


31-0 


no-8 


3 2 '4 


i°4'S 


26-5 


987 


21-8 


76-9 


187 


60 -6 


14-0 



256 



PROFESSOR C. PIAZZI SMYTH ON 



Tables XXVII. and XXVIII ; or " FROST AND FIRE " IN EACH MONTH ; OR THE 

FROST, AND BY DAY FOR FIRE, i.e., SOLAR 
Table XXVII. represents " Frost " only, being the Maximum Depression in each Month by Night 

REPRESENTS " FlRE " OR SOLAR RADIATION ONLY, BEING THE MAXIMUM ELEVATION IN EACH 

Table XX VII.— "FROST." 



Year. 


January. 


February. 


March. 


Ap 


il. 


May. 


June. 


July. 


Obsd. 


Sueces. 1 
Menus. 


Obsd. 


Sueces. 
Weans. 


Obsd. 


Sueces. 
Means; 


Obsd. 


Sueces. 
Means. 


Obsd. 


Sueces. 
Means. 


Obsd. 


Sueces. 
Means. 


Obsd. 


Sueces. 
Means. 


1856 






























1857 


-19-6 




-11-0 




-12-2 




- 9-2 




- 4-2 




+ 0-3 




+ 1-9 




1858 


-14-6 




-21-5 




-18-8 




-15-6 




- 6'8 




+17 




+ 1-5 




1859 


-15-4 


-17-1 

-i6-s 


-17-4 


- l6 - 2 

-16-6 


-14-8 


-*S\5 

-i5"3 


-14-9 


— 12 "4 
-13' 2 


- 9'4 


-5'5 
-6'8 


-1-9 


+ i-o 

O'O 


+ 0-2 


+ l'7 
+ 1-2 


1860 


-19-4 




-28-7 




-14-0 




-11-2 




- 5'1 




+ 0-2 




+ 4-4 




1861 


-24-5 


- I7'2 


-17-4 


— 19*6 


- 7-8 


-15-0 


-10-7 


- 127 


-11-6 


-6' 4 


+ 37 


+o-i 


+ 4-4 


+ 2'0 


1862 


- 8-8 


-187 


-16-5 


- 19*2 


-21-0 


-13 '5 


-10-8 


-12-3 


- 5-6 


-7'4 


-1-1 


+ o-8 


+2-3 


+ 2 'S 


1863 


-107 


- 17 'O 


-10-5 


-l8'8 


-12-4 


-14-8 


- 7-9 


— I2"I 


- 5-8 


-7'i 


-0-6 


+ o'5 


-3-9 


+ 2 '4 


1864 


-20-2 


-i6-i 
-16 '6 


-23-2 


- 17*6 
-18-3 


-19-3 


-14-4 
-15-0 


- 7-5 


-ii'S 

- II'O 


- 69 


-6-9 
-6' 9 


-4-3 


+ 0-3 

-0'2 


+ 3-3 


+ i'S 
+ 1-8 


1865 


-23-5 




-24-6 




-13-8 




-10-1 




- 5-8 




-1-0 




+0-6 




1866 


-18-8 


-17 '4 


-17-8 


- i9'o 


-21-8 


-14-9 


-12-9 


— io'9 


-11-1 


-6'8 


-4-6 


-°'3 


+2-2 


+ i-6 


1867 


-25-8 


-17 "6 


-14-3 


-18-9 


-21-0 


-15-6 


- 6-8 


- ii'i 


- 6-6 


- 7 '2 


-0-4 


-o-8 


+ 0-9 


+ i'7 


1868 


-17-2 


-i8-3 


-10-6 


-i8-4 


-11-5 


-16-1 


-10-2 


— 107 


- 8'1 


- 7 '2 


+1-0 


-07 


+ 3-8 


+ r6 


1869 


-131 


-18-2 
-17-8 


- 8-0 


-17-8 

- 17 'O 


-13-3 


-157 
-i5"5 


-12-5 


-io'6 

-io-8 


-10-4 


- 7 '2 

-7'S 


-4-5 


-o-6 
-0-9 


+4-0 


+ r8 

+ 2 - 


1870 


-15-7 




-20-6 




-16-2 




- 76 




- 6'1 




+2-3 




+ 4-5 




1871 


-18-5 


-177 


-10-9 


-17 '3 


-15-2 


-iS-6 


-11-4 


-10 "6 


-11-0 


-7 '4 


-3-1 


-07 


+ 3-5 


+ 2"2 


1872 


-13-2 


-177 


- 9-6 


- 16 '9 


-13-8 


-iS'S 


- 8-6 


-io - 6 


- 87 


-7-6 


-1-6 


-o-8 


+0-2 


+ 2'2 


1873 


-15-3 


-17-4 


-21-5 


-164 


-123 


-iS - 4 


-11-6 


-10-5 


-10'8 


-77 


-1-5 


-0-9 


+ 2-6 


+ 2-1 


1874 


-11-0 


-i7'3 
— 17 'O 


-16-2 


— 167 
— 167 


-15-6 


-i5'3 
-iS"3 


- 8-1 


- io"6 
— 10 "4 


- 9'4 


~T9 

-8'0 


-4-4 


-0-9 
- i'i 


+ 37 


+ 2-1 
+ 2 - 2 


1875 


-19-0 




-177 




-13-9 




-11-4 




- 3-9 




-2-1 




-0-4 




1876 


-17 3 


-17-1 


-167 


- 167 


-15-2 


-iS' 2 


-14-8 


-io'S 


- 9'8 


-7'8 


-07 


- 1 "a 


+ 3-0 


+ 2-1 


1877 


-17-9 


-17-1 


-16-2 


— 167 


-16-2 


-IS' 2 


-11-7 


- 107 


-11-9 


-7'9 


+ 1-5 


— i'i 


+ 3-6 


+ 2'I 


1878 


-16-4 


-17-1 


- 9-6 


-167 


-16 3 


-IS' 2 


-11-9 


— 107 


- 5-5 


-8'o 


-3-9 


— I'O 


+ 2-9 


+ 2'2 


1879 


-23-6 


-17-1 
-i7'4 


-19-9 


- 16 '4 
-16-5 


-18-1 


-iS'3 

-iS'4 


-12-2 


-io-8 
- io'9 


-12-4 


-7'9 

-8'i 


-2-1 


- i'i 

— i'a 


+ 3-5 


+ 2'2 
+ 2-3 


1880 


-IP -4 




-10-4 




-13-4 




-10-6 




- 9-2 




-5-3 




+ 1-8 




1881 


-34-1 


I7'S 


-19-0 


-16-3 


-23-4 


-IS'3 


-15-6 


- io'8 


- 7-5 


-8'2 


-6-8 


-i'4 


+ 1-2 


+ 2 - 3 


1882 


-107 


-18-1 


- 8-8 


- i6'4 


- 8-3 


-i5'7 


-133 


- II'O 


- 6'9 


-8-i 


-2-3 


-i-6 


+ 5-0 


+ 2'2 


1883 


-12-8 


-17-8 


-10-2 


-i6'i 


-16-7 


-iS'4 


- 8-8 


- ii'i 


- 9'3 


-8-1 


-2-5 


-i-6 


+ 1-5 


+ 2'3 


1884 


-13-0 


- iy'6 
'7'5 


-12-6 


-iS'9 
-i S -8 


-10-3 


->5'4 
-IS' 2 


-10-8 


-II'O 
-II'O 


- 6-6 


-8-1 
-8-2 


-1-4 


-i-6 
-r6 


+ 0-5 


+ 2'3 
+ 2 - 2 


1885 


-17 5 




-19-1 




-14-4 




-11-2 




- 87 




-3-3 




+ 1-5 




1886 


-27 


-I7-5 


-20-3 


-iS'9 


-21-4 


-i5' 2 


-10-5 


1 1 'O 


- 87 


-8-i 


-37 


-i'7 


+ 0-6 


+ 2'2 


1887 


-17 -2 


-17-8 
-17-8 


-15-0 


- i6 - o 
- 16 "O 


-17-6 


-i5'4 
-iS'5 


-121 


- II'O 

- II'O 


- 7-9 


-8'i 
-8'i 


-1-6 


-i'7 
-i'7 


-1-0 


+ 2'2 
+ 2-1 



MEAN SCOTTISH METEOROLOGY. 



257 



EXTREMES OF THE EXPOSED BLACK-BULB THERMOMETERS, BY NIGHT FOR 
RADIATION, BELOW AND ABOVE 32° F. 

of the Mean of all the exposed Black-Bulb Thermometers below 32° F. ; while Table XXVIII. 
Month, by Day, of the Mean of all the exposed Black-Bulb Thermometers above 32° F. 

Table XXVII.—" FROST." 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 

Quantities in 

each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Succes. 


Obsd. 


Succes. 


Obsd. 


Succes. 


Obsd. 


Succes. 


Obsd. 


Succes. 




Means. 




Means. 




Means. 




Means. 




Means. 
































1856 


+2-5 




+ 1-0 




- 7-1 




-13 8 




*■ 9-6 




- 6-8 




1857 


+0-8 


+ 1-6 


-3-2 


— 1*1 


-10-0 


- 8-6 


-20-0 


- 16 '9 


-13-4 


-II'S 


-100 


- 8-4 


1858 


+0-9 


+ i - 4 


-5-3 


-2'5 


-19-7 


-12-3 


-14-8 


-l6 - 2 


-29-2 


-17-4 


-11-8 


- 9"5 


1859 


+0-8 


+ 1-2 


-5-8 


"3'3 


- 9-2 


-"'5 


-14-8 


-15-8 


-31-5 


-20"9 


-11-2 


- IO'O 


1860 


+ 4-4 


+ 1-9 


-1-8 


-3'° 


- 6-8 


- io - 6 


-17-9 


-16-3 


-150 


-197 


- 8-4 


- 9-6 


1861 


+2-2 


+ i-9 


-3-1 


-3"o 


- 77 


-IO - I 


-17-0 


- 16 - 4 


- 7-8 


-i 7 '8 


- 7'9 


- 9-4 


1862 


-0-8 


+ i'S 


-2-4 


-2' 9 


- 9-7 


-IO'O 


-13-6 


-i6'o 


-16 2 


-17'S 


- 7-9 


- 9'i 


1863 


2-1 


+ i-i 


-1-0 


-27 


- 9-5 


-IO'O 


-12-1 


-i5\5 


-13-0 


-iyo 


- 9-6 


- 9'2 


1864 


-0-3 


+ 0-9 


+ 0-4 


-2-4 


-11-9 


- IO*2 


-13 5 


-I5-3 


-104 


-162 


- 9-6 


- 9'2 


1865 


+ 0-4 


-t-o'9 


-26 


-2-4 


- 8-4 


-IO'O 


-13-3 


-iS'i 


-11-9 


-IS* 


-10-0 


- 9'3 


1866 


+2-9 


+ ri 


-1-8 


-2'3 


- 8-8 


- 9'9 


-11-0 


-147 


-139 


-15-6 


- 8-9 


- 9'3 


1867 


+ 3-4 


+ i'3 


-2-8 


-2-4 


- 9-9 


- 9'9 


-14-5 


-147 


-13-3 


-iS'4 


- 7-5 


- 9'i 


1868 


-5-5 


+07 


-3'0 


-2-4 


- 9-9 


- 9"9 


-17-5 


-14-9 


-22-4 


— i6'o 


- 9-7 


- 9-2 


1869 


+0-8 


+07 


-3-4 


-2-5 


- 7-6 


- 97 


-12-9 


-14-8 


-26-2 


- 167 


- 9-1 


- 9-2 


1870 


+2-6 


+o - 9 


-7-3 


-2-8 


-10-2 


- 9-8 


-15-4 


-14-8 


-17-1 


— 167 


- 9-5 


- 9-2 


1871 


o-o 


+ 0-8 


-6-0 


-3'° 


-12-1 


- 9'9 


-11-0 


-i4"6 


-16-7 


-167 


- 8-4 


- 9'i 


1872 


o-o 


-f-o-8 


-37 


-3'i 


-11-0 


-IO'O 


-12-3 


-14-4 


-11-6 


— 16 "4 


- 91 


- 9-1 


1873 


+ 0-4 


+ 07 


-20 


-3'° 


- 8-3 


- 9'9 


-12-7 


-14 '3 


-24-9 


-i6 - 9 


- 9-0 


- 9-1 


1874 


+ 2-9 


+ 0-9 


-2-1 


-2-9 


- 8-0 


- 9-8 


-17-1 


-I4'S 


-18-1 


— 17 - o 


- 9-2 


- 9-1 


1875 


+0-3 


+ o-8 


-2-0 


-2-9 


- 5-0 


- 9'5 


-15-2 


-i4\5 


- 99 


-i6'6 


- 8-6 


- 9'i 


1876 


-0-2 


+ o-8 


-4-2 


-3'° 


- 9-7 


- 9'5 


-10-9 


-i4'3 


-16-0 


-i6'6 


- 9-2 


- 9-1 


1877 


+3-3 


+ 0-9 


o-o 


-2-8 


- 7'5 


- 9'5 


-14-0 


-i4'3 


-25-8 


— 17 '0 


- 87 


- 9-1 


1878 


+ 1-5 


+0*9 


-4-5 


-2-9 


-114 


- 9 - S 


-16-1 


-14-4 


-29-1 


-17 '5 


-12'0 


- 9-2 


1879 


+2-1 


+ i-o 


-3-7 


-2-9 


-18-0 


- 9"9 


-24-8 


-14-8 


-22-5 


-177 


-11-1 


- 9'3 


'1880 


-4-2 


+ o'8 


-3-7 


-3'° 


-12-7 


— IO'O 


-10-9 


-147 


-15-8 


-177 


-12 -7 


- 9-4 


1881 


+ 1-3 


+ o-8 


-4-5 


-3'° 


-10-4 


- IO'O 


-13-4 


— 14 '6 


-26-9 


-i8'o 


- 8-3 


- 9"4 


1882 


+4-2 


+ 0-9 


-2-8 


-3'° 


- 7-6 


- 9'9 


-13-8 


-i4 - 6 


-11-5 


-17-8 


- 7-5 


- 9'3 


1883 


+ 1-6 


+ 0-9 


-1-8 


-3'° 


- 8-4 


- 9'9 


-17-6 


-147 


-16-9 


-177 


- 8-1 


- 9'3 


1884 


-22 


+ o-8 


-9-5 


-3' 2 


-13-9 


-IO'O 


-18-4 


-14-8 


-19-8 


-17-8 


-11-4 


- 9"4 


1885 


+ 1-2 


+ o-8 


-4-5 


-3' 2 


- 5'0 


- 9-8 


- 7-5 


— 14"6 


-22-8 


-180 


-10-8 


- 9'4 


1886 


+ 0-4 


+ o-8 


-5-5 


-3'3 


-10-2 


- 9-9 


-13-3 


-i4'6 


-18-0 


-i8'o 


- 9-9 


- 9-4 


1887 



VOL. XXXV. PART 3. 



2 U 



258 



PROFESSOR C. PIAZZI SMYTH ON 



Tables XXVIT. and XXVIII.; or "FROST AND FIRE" IN EACH MONTH; OR THE 

FROST, AND BY DAY FOR FIRE, i.e., SOLAR 
Table XXVII. represents "Frost" only, being the Maximum Depression in each Month by Night 

REPRESENTS " FlRE," OR SOLAR RADIATION ONLY, BEING THE MAXIMUM ELEVATION IN EACH 

Table XXVIII.—" FIRE." 



Year. 


January. 


February. 


March. 


Ap 


11. 


May. 


June. 


July. 
































Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


1856 






























1857 


+ 47-0 




+ 55-7 




+ 56-9 




+ 61-1 




+ 73-0 




+ 91-6 




+ 807 




1858 


+35-7 




+ 49-8 




+ 64-8 




+ 77'0 




+72-8 




+ 88-8 




+ 82-1 




1859 


+40-0 


+4i*4 


+ 46 2 


+ 52-8 


+ 527 


+ 6o-8 


+61-4 


+ 69-0 


+79-4 


+ 72-9 


+84-1 


+ 9°'2 


+77-5 


+ 81-4 




+ 36-0 


+ 40 -g 


+ 48-6 


+ 50 -6 


+54-5 


+ 58-1 


+ 66-5 


+ 66-5 


+74-2 


+ 75 'I 


+ 70-6 


+ 88-2 


+ 78-2 


+ 8o-i 


1860 




+ 397 




+50-1 




+ 57 '2 




+ 66-5 




+ 74'8 




+ 8 3 '8 




+ 79-6 


1861 


+ 33-6 




+41-9 




+ 48-3 




+657 




+69-3 




+ 80-2 




+ 74-3 




1862 


+ 36-7 


+ 38-5 


+ 45-5 


+ 48-4 


+53-1 


+ 55 '4 


+60-8 


+ 66-3 


+ 65-6 


+737 


+ 70-2 


+ 83-1 


+ 67-0 


+ 78-6 


1863 


+ 30-7 


+ 38 -2 


+ 40-3 


+ 48-0 


+ 49-0 


+ 55'° 


+ 547 


+ 65'4 


+ 62-6 


+ 72'4 


+ 68-6 


+ 80-9 


+ 77-5 


+ 76-6 


1864 


+ 34-5 


+ 37'i 


+40-8 


+ 46-9 


+ 49-2 


+ 54'2 


+ 64-8 


+ 63-9 


+74-2 


+ 71*0 


+ 707 


+ 79-2 


+ 80-2 


+ 76'8 




+ 30-7 


+ 36-8 


+ 41-1 


+ 46-1 


+51-0 


+ 53 - 6 


+ 70-1 


+ 64-0 


+77-2 


+ 71 + 


+ 80-2 


+ 78-1 


+ 79-6 


+ 77 "2 


1865 




+ 36-1 




+ 45 "5 




+ 53 '3 




+ 647 




+ 72-0 




+ 78'3 




+ 77'5 


1866 


+ 325 




+ 44-4 




+51-8 




+ 63-5 




+ 70-9 




+ 81-4 




+ 81-2 




1867 


+ 34-2 


+ 357 


+ 47-4 


+45 '4 


+52-6 


+ 53'i 


+ 58-6 


+ 64-6 


+ 68-3 


+71-9 


+ 78-1 


+ 78'6 


+ 79-5 


+ 77'8 


1868 


+ 33-0 


+ 35-6 


+417 


+ 45 '6 


+ 57'2 


+ 53'i 


+61-3 


+ 64-0 


+ 68-5 


+ 71-6 


+ 78-6 


+ 78'6 


+ 85-1 


+ 78-0 


1869 


+ 317 


+ 35'4 


+ 43-1 


+ 45 "3 


+53-6 


+ 53'4 


+ 69-6 


+ 63-8 


+ 687 


+ 7i'3 


+ 767 


+ 78-6 


+ 82-3 


+ 78'6 




+ 31-2 


+ 35'i 


+ 41-1 


+ 45 'i 


+55-2 


+ 53 "4 


+ 65-4 


+ 64-2 


+ 74-0 


+7i"i 


+ 80-6 


+ 78'4 


+ 86-6 


+ 78'9 


1870 




+ 34-8 




+ 44-8 




+ 53'° 




+ °4 '3 




+ 7i'3 




+ 78'6 




+ 79 '4 


1871 


+28-9 




+ 43-1 




+60-3 




+67-2 




+ 81-1 




+ 83'0 




+ 82-5 




1872 


+ 33-6 


+ 34'4 


+43-8 


+ 447 


+56-1 


+ 54'° 


+63-0 


+ °4'S 


+ 70-4 


+ 72-0 


+ 78-9 


+ 78'9 


+ 88-0 


+ 79-6 


1873 


+31-8 


+ 34 '4 


+ 44-9 


+ 44 "6 


+52-9 


+ 54" 1 


+68-9 


+ 64-4 


+ 76-0 


+ 71 '9 


+81-0 


+ 78'9 


+ 83-5 


+ 8o-i 


1874 


+32-9 


+ 34'2 


+44-0 


+ 447 


+52-8 


+ 54'i 


+ 70-5 


+ °47 


+ 72-5 


+ 72T. 


+80-6 


+ 79'° 


+ 84-5 


+ 80-3 




+32-8 


+ 34'2 


+38-9 


+ 44 '6 


+527 


+ 54'° 


+ 69-0 


+ 65-0 


+ 66-2 


+ 72-2 


+ 74-1 


+ 79'i 


+ 81-5 


+ 80 -6 


1875 




+ 34'i 




+44'3 




+ 53 '9 




+ 65-2 




+ 7i'8 




+ 78-8 




+ 80 -6 


1876 


+36-4 




+ 43-0 




+49-2 




+ 67-4 




+ 71-8 




+ 84-4 




+ 85-5 




1877 


+32-7 


+ 34"2 


+ 38-0 


+44'3 


+ 54-6 


+ 537 


+ 56-0 


+ °5 '3 


+65-1 


+ 71 "8 


+78-9 


+ 79'i 


+ 70-6 


+ 80-9 


1878 


+36-2 


+ 34'i 


+44-5 


+44'° 


+ 557 


+ 537 


+ 64-9 


+ 64 '9 


+72-3 


+ 7i'5 


+82-6 


+ 79'i 


+ 85-2 


+ 80-4 


1879 


+34-1 


+ 34'2 


+ 417 


+ 44'° 


+ 52-5 


+ 53 '8 


+62-6 


+ 64-9 


+70-0 


+71-6 


+73-6 


+ 79 "3 


+77-6 


+ 80 -6 




+ 35-9 


+ 34"2 


+ 44-2 


+ 43 '9 


+ 59-0 


+ 53'8 


+ 661 


+ 64-8 


+ 75-0 


+ 7i"5 


+ 81-3 


+ 79'° 


+ 83-6 


+ 80-5 


1880 




+ 34 - 3 




+ 43 '9 




+ 54'° 




+ 64-8 




+ 71-6 




+79'* 




+ 8o'6 


1881 


+ 36-8 


+ 34 '4 


+ 47-5 




+ 59-9 




+647 




+ 84-5 




+86-0 




+ 75-6 




1882 


+ 34-7 


+ 34 '4 


+ 471 


+ 44'° 


+55-1 


+ 54'2 


+65-3 


+ 64-8 


+ 79-1 


+ 72-1 


+80-1 


+ 79 "4 


+81 -2 


+ 80-4 


1883 


+ 32-4 




+ 41-5 


+ 44'2 


+ 537 


+ 54 '3 


+ 617 


+ 64-8 


+ 71-3 


+ 72-4 


+ 77-8 


+ 79 '4 


+ 80-4 


+ 80-4 


1884 


+ 30-7 


+ 34 - 3 


+ 43-6 


+ 44'i 


+53-9 


+ 54 '2 


+ 63-6 


+ 647 


+ 73-8 


+ 72'4 


+ 80-5 


+ 79'4 


+767 


+ 80-4 




+ 26-4 


+ 34'2 


+ 43-2 


+ 44 '0 


+55-1 


+ 54 '2 


+ 637 


+ 647 


+ 64-8 


+ 72-4 


+ 78-6 


+ 79'4 


+ 84-4 


+ 80-3 


1885 




+ 33 '9 




+ 44 "o 




+ S4 - 3 




+ D47 




+ 72 '2 




+ 79 '4 




+ 80-4 


1886 


+33-2 




+ 43-8 




+55-8 




+ 65-4 




+ 69-4 




+ 79-1 




+ 80-0 




1887 


+ 35-5 


+ 33 '9 
+ 34'° 


+ 49-5 


+ 44'° 
+ 44"2 


+ 57-8 


+ 54 '3 
+ 54 "4 


+ 637 


+ 647 
+ °47 


+727 


+ 72'I 
+ 72'I 


+ 90-4 


+ 79 '4 
+ 797 


+ 85-0 


+ 80-4 
+ 80 -6 



MEAN SCOTTISH METEOROLOGY. 



259 



EXTREMES OF THE EXPOSED BLACK-BULB THERMOMETERS, BY NIGHT FOR 
RADIATION, BELOW AND ABOVE 32° F. 

of the Mean of all the exposed Black-Bulb Thermometers below 32° F. ; while Table XXVIII. 
Month, by Day, of the Mean of all the exposed Black-Bulb Thermometers above 32° F. 

Table XXVIII.—" FIRE." 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 
Quantities in 
each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


























1856 


+ 857 




+72-6 




+ 62-4 




+ 49-3 




•+41-1 




+ 64-8 




1857 


+ S4-2 




+78-8 




+ 62 5 




+ 48-3 




+36-9 




+ 651 




1858 


+ 79-3 


+ 8 5 -o 
+ 8 3 -i 


+ 71-6 


+ 75*7 
+ 74 "3 


+ 64-2 


+ 62-4 
+ 63-0 


+ 44-1 


+48-8 

+ 47 '2 


+ 31-5 


+ 39'° 
+ 3°-5 


+ 61-0 


+ 65-0 
+ 63-6 


1859 


+ 77-1 




+72-4 




+58-5 




+ 43-3 




+ 31-8 




+59-3 




1860 


+66-2 


+ 8i-6 


+687 


+ 73'8 


+57 '2 


+ 61-9 


+ 41-2 


+ 46-2 


+347 


+ 35'3 


+ 56-8 


+ 62-6 


1861 


+ 72-6 


+ 78-5 


+ 74-1 


+ 72-8 


+61-6 


+ 6ro 


+ 41-4 


+ 45 '2 


+ 30-1 


+ 35'2 


+56-6 


+ 61-4 


1862 


+73-3 


+ 77 '5 


+64-6 


+ 73'° 


+ 520 


+ 6ri 


+39-9 


+ 44 '6 


+ 30-0 


+ 344 


+53-6 


+ 60 -6 


1863 


+ 75-3 


+ 76-9 
+ 767 


+ 66 3 


+ 71-8 
+71M 


+59-2 


+ 59-8 
+ 597 


+ 42-1 


+ 43 '9 
+ 437 


+ 29-0 


+ 337 
+ 33' 1 


+57-2 


+ 59'° 
+ 59 '3 


1864 


+73-5 




+ 74-3 




+ 65-8 




+ 44-6 




+36-0 




+ 60 3 




1865 


+711 


+ 76 + 


+66-4 


+ 7i\5 


+61-9 


+ 6o - 4 


+ 45-9 


+ 43-8 


+33 2 


+ 33 "5 


+ 587 


+ 59 '4 


1866 


+78-1 


+ 75'8 


+67-2 


+71 - o 


+54-5 


+60-5 


+ 45-5 


+ 44 '° 


+31-2 


+ 33 '4 


+57-9 


+ 59 "3 


1867 


+ 83-9 


+ 76-0 


+70-0 


+ 70-6 


+53-9 


+ 6o - o 


+37-3 


+44'* 


+30-8 


+ 33 '2 


+ 58-4 


+ 59 '2 


1868 


+ 79-2 


+767 
+ 76-9 


+ 68-7 


+7<r6 
+ 70-4 


+60-7 


+59 '5 
+ 59-6 


+38-0 


+ 43 '° 
+ 43'i 


+27-5 


+ 33'° 
+ 32-6 


+ 58-3 


+59'"" 

+ 59'i 


1869 


+ 86 -9 




+70-5 




+ 63-9 




+ 44-5 




+29-1 




+ 60-8 




1870 


+ 85-4 


+ 77-6 


+ 76-4 


+ 7° '4 


+ 58-3 


+ 59 "9 


+ 41-9 


+43 -2 


+31-5 


+ 3 2- 4 


+61-6 


+ 59'2 


1871 


+ 82-3 


+ 78-1 


+ 70-0 


+ 70-8 


+55-6 


+ 59-8 


+ 43-1 


+43 '2 


+ 28-7 


+ 3 2 '3 


+ 59-5 


+ 59 '4 


1872 


+74-3 


+ 78-4 


+ 73-2 


+ 70-8 


+ 57-3 


+ 59 '5 


+37-6 


+ 43 '2 


+ 29-2 


+ 32-1 


+ 59-2 


+ 59 '4 


1873 


+ 76-7 


+ 78-1 
+ 78-1 


+ 67-3 


+ 7°'9 
+ 707 


+53-5 


+ 59 '4 
+ 59'i 


+39-3 


+ 42-8 
+42 '6 


+257 


+3 1 '9 

+31-6 


+58-4 


+ 59 '4 
+ 59 '3 


1874 


+ 79 '2 




+ 73-4 




+51-7 




+ 40-0 




+29-4 




+ 57-4 




1875 


+ 85-0 


+ 78-1 


+72-7 


+ 70 '9 


+60-9 


+ 587 


+48-4 


+ 42-5 


+30-6 


+3i'4 


+ 61-3 


+ 59 '2 


1876 


+ 72-2 


+ 78-S 


+ 69-8 


+71 'o 


+59-8 


+ 58-8 


+ 45-2 


+ 42-8 


+30-6 


+ 3i'4 


+561 


+ 59 '3 


1877 


+ 83-7 


+ 78-2 


+ 75-7 


+ 7°'9 


+61-7 


+ 58-8 


+ 42-3 


+ 42-9 


+ 31-9 


+3 I- 4 


+ 61-4 


+ 59 '2 


1878 


+ 78-3 


+ 78-4 
+ 78 + 


+ 73-7 


+71 "I 

+ 71 '2 


+67-0 


+ 59-0 
+ 59 "3 


+50-2 


+42 - 9 
+43-2 


+ 29-1 


+ 3i '4 
+ 3i'3 


+ 59-2 


+ 59'3 
+ 59 '3 


1879 


+ 857 




+ 80-7 




+ 62-5 




+ 44-4 




+337 




+627 




1880 


+77-6 


+ 787 


+73-2 


+ 71-6 


+62-1 


+ 59 '4 


+ 44-7 


+43 "2 


+ 30-4 


+ 3 J '4 


+ 61-9 


+ 59 '4 


1881 


+85-2 


+ 787 


+ 72-1 


+ 717 


+56 9 


+ S9"5 


+ 41-0 


+ 43 '3 


+26-3 


+ 3i'3 


+ 60-3 


+ 59'5 ; 


1882 


+78-3 


+ 78-9 


+ 72-3 


+ 717 


+63-4 


+ 59 '4 


+ 45-8 


+ 43 "2 


+29-4 


+ 31-2 


+ 59-0 


+ 59'5 


1883 


+ 80-0 


+ 78-9 
+ 78-9 


+ 73-2 


+ 717 
+ 71-8 


+617 


+ 59-6 
+ 597 


+37-9 


+ 43 '3 
+ 43' 1 


+25 '4 


+ 31-1 
+ 3° '9 


+ 58-4 


+ 59 '5 
+ 59 '5 


1884 


+ 76-4 




+ 70-1 




+53-6 




+38-9 




+34-0 




+57-4 




1885 


+76'0 


+ 78-9 


+73-6 


+ 717 


+62-3 


+ 59'5 


+45-6 


+ 43'° 


+29-0 


+ 31-0 


+59-4 


+ 59'4 


1886 


+78-8 


+78-8 
+ 78-8 


+72-5 


+ 71-8 
+ 71-8 


+66-7 


+ 59-6 
+ 59-8 


+ 44-9 


+ 43' 1 
+43 - " 1 


+28-6 


+ 3° '9 
+ 3° "9 


+62-2 


+ 59 '4 
+ 59'5 


1887 



•260 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXIX.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Wind Force per Month. 



Year. 


January. 


February. 


March. 


AprU. 


May. 


June. 


July. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 

Menus. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


1856 


37-82 




63-80 




51-15 




29-40 




30-07 




57-00 




41-54 




1857 


38-75 




49-56 




58-28 




35-40 




24-49 




19-50 




48-05 




1858 


73-16 


3 8-28 


50-40 


56-68 


58-59 


54-72 


43-50 


32-40 


41-54 


27-28 


40-80 


38-2S 


34-41 


44-80 


1859 


91-45 


49-91 
60-30 


74-76 


54"59 
59-63 


98-89 


56-OI 

6673 


69-90 


36-10 

44'55 


26-04 


32-03 
30-54 


49-80 


39-10 

4178 


44-64 


4I-33 
42-16 


1860 


55-18 




67-57 




60-45 




46 50 




44-02 




38-40 




26-97 




1S61 


41-23 


59 "27 


62-16 


6l "22 


81-84 


65'47 


33-90 


44-94 


36-58 


33-23 


26-40 


41-10 


43-71 


39-12 


1862 


52-08 


56-27 


38-08 


61-37 


42-16 


68-20 


47-10 


43-io 


39-37 


3379 


50-10 


38-65 


54-56 


39-89 


1863 


61-38 


55 '67 


53-20 


58-05 


47-74 


64-48 


56-10 


43'67 


35-34 


34-59 


31-50 


40-29 


31-93 


41-98 


1864 


47-74 


56-38 
55 "42 


37 99 


57'44 

55-28 


45-57 


62-39 
60-52 


30-60 


45 '23 
43-60 


35-03 


34-68 
3472 


43-80 


39-19 
397° 


35 65 


40-73 
40-16 


1865 


61-07 




35-84 




50-22 




36-60 




45-88 




33-30 




30-38 




1866 


67-58 


55*99 


52-92 


53 "34 


45-88 


59 '49 


46-20 


42-90 


32-55 


35-84 


25-80 


39-o6 


27-90 


39-i8 


1867 


44-33 


57 '°4 


59-64 


53'3° 


50-53 


58-25 


55-20 


43-20 


40-61 


35 '54 


29-40 


37-85 


32-24 


38-16 


1868 


59-52 


55-98 


93 09 


S3-83 


66-03 


57 '61 


46-80 


44-20 


46-19 


35-96 


47-40 


37-I5 


2914 


37 '66 


1869 


5673 


56 '25 

56-29 


57-40 


56-85 
56% 


44-33 


58-26 
57-26 


42-00 


44'4o 
44-23 


44-64 


36-75 
37'3i 


32-40 


37'94 
37'54 


39-68 


37-01 
37-20 


1870 


32-24 




47-60 




40-61 




49-80 




45-57 




33-60 




32-55 




1871 


42-16 


54-68 


39-36 


56-27 


57-97 


56-iS 


40-80 


44-60 


34-72 


37-86 


32-10 


37-28 


34-41 


36-89 


1872 


6603 


53 "9° 


55-97 


56-46 


55-80 


56-26 


64 20 


44-36 


49-29 


37 '66 


35-40 


36-96 


35-65 


36-74 


1873 


63-86 


54 '62 


38-08 


56-43 


40-30 


56-24 


44-10 


45 "S3 


38-13 


38-35 


39-60 


36-86 


33-79 


36-67 


1874 


69-44 


5S - i3 
55-88 


36-40 


5S-4I 
54'4i 


71-30 


55'35 
56-I9 


49-80 


45-45 
45-68 


40-92 


38-34 
38-47 


45-30 


37-02 
37 '45 


35-03 


36-51 
36-43 


1875 


54-25 




38-92 




45-26 




30-60 




35-65 




33-00 




33-79 




1876 


73-47 


55-8o 


53-36 


S3-64 


93-31 


55'64 


59-10 


44-92 


45-26 


38-33 


51-60 


37-23 


64-17 


36-30 


1877 


93-31 


56-64 


83-16 


53'62 


68-20 


57-44 


81-90 


45-6o 


73-47 


38-66 


60-90 


37 '91 


57-35 


37-63 


1878 


59-52 


58-3I 


47-88 


54'97 


75-02 


57% 


47-70 


47-25 


56-11 


40-24 


38-10 


38-96 


39-37 


38-52 


1879 


53-94 


58-3° 
58-18 


47-04 


54-66 
54-34 


92-38 


58-67 
60 -08 


53-10 


47-27 
47-5I 


52-08 


40-93 
41-40 


40-50 


38-92 
38-99 


62-00 


38-S6 
39 '54 


1880 


56-42 




87-00 




43-09 




61-80 




62-62 




45-60 




34-41 




1881 


39-37 


58-11 


54-32 


55-65 


88-97 


59-40 


56-10 


48-08 


58-90 


42-25 


60-30 


39'25 


62-93 


39 '33 


1882 


90-52 


57-39 


79-24 


5S'6o 


113-15 


60-53 


74-10 


48-39 


50-53 


42-89 


51-30 


40 '06 


46-19 


40-24 


1883 


90-21 


58-61 


111-72 


56-47 


92-69 


62-48 


64-80 


49-34 


78-43 


43' 1 7 


47-40 


40-48 


48-36 


40-46 


1884 


121-52 


59-74 
61-87 


92-51 


S8-44 
59-62 


71-92 


63-56 
63-85 


44-10 


49-90 
4970 


65-41 


44-43 
45*15 


47-70 


40-72 
40-97 


37-20 


40-74 
40-62 


1885 


72-85 




75-60 




89-59 




69-90 




69-13 




49-20 




41-85 




1886 


93-69 


62-24 


42-28 


60-15 


80-29 


6471 


78-60 


50-37 


64-48 


45-95 


65-70 


41-24 


69-13 


40-66 


1887 


85-56 


63'25 
63-95 


66-64 


59-S8 
59-8o 


56-11 


65-21 
64-93 


58-80 


51-28 
51-52 


61-38 


46-5S 
47-01 


41-10 


42-03 
42-00 


53-63 


4i-58 
41-96 



MEAN SCOTTISH METEOROLOGY. 



261 



Table XXIX. continued.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Wind Force per Month. 



August. 


September. 


October. 


November. 


December. 


Mean Month 


Successive 
























of Observed 
Quantities in 
each Year. 


Means of the 

Accumulating 

Years. 


Year 
repeated. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 

Means. 


Obsd. 


Succes. 
Means. 


Obsd. 


Succes. 
Means. 


31-31 




50-70 




27-28 




29-10 




57-97 




42-26 




1856 


32-24 




41-40 




39-99 




33-00 




71*2 




41-05 




1857 


30 69 


3178 


50-40 


46-05 


58-90 


33-64 


32-70 


31 '05 


55-80 


64-94 


47-57 


41-66 


1858 


48-98 


31 '41 

3S'8o 


54-00 


47-50 
49-12 


50-53 


42-06 
44-18 


39-30 


31-60 
33 '52 


51-77 


61-90 
59-36 


58-34 


43-63 
47-30 


1859 


35-65 




32-70 




72-54 




32-70 




42-47 




46-26 




1860 


59-52 


3577 


41-40 


45-84 


39-68 


49-85 


70-80 


33-36 


37-20 


55-99 


47-87 


47-10 


1861 


25-42 


3973 


27-60 


45"io 


64-17 


48-I5 


24-00 


39-60 


66-65 


52-86 


44-27 


47 '22 


1862 


35-34 


37 "69 


50-70 


42 '6o 


45-26 


SO'44 


41-10 


37-37 


74-09 


54-83 


46-97 


46-80 


1863 


33-79 


37 '39 
36 - 99 


45-00 


43 '61 
43'77 


38-75 


49'79 
48-57 


33-90 


37-84 
37-40 


40-61 


57-23 

55-39 


39-04 


46-82 
45'96 


1864 


27-28 




37-50 




53-63 




31-80 




77-50 




43-42 




1865 


35-96 


36-02 


40-80 


43-14 


32-86 


49-07 


53-40 


36-84 


55-80 


57'6o 


43-14 


45'70 


1866 


30-07 


36-02 


43-80 


42-93 


42-47 


47-6o 


30-90 


38-35 


49-60 


57'43 


42-40 


45'47 


1867 


49-60 


35'52 


36 30 


43-oo 


50-84 


47-17 


41-10 


3772 


52-39 


5678 


51-53 


45-22 


1868 


35-96 


36-60 
36"56 


57-00 


42-48 
43-52 


50-22 


47'45 
47-65 


57-60 


37 "98 
39-39 


57-35 


56-44 
56-51 


47-94 


4570 

45-86 


1869 


26-04 




33-90 




46-50 




31-20 




39-68 




38-27 




1870 


39-06 


35-86 


31-20 


42-88 


44-02 


47'57 


40-80 


38-84 


50-84 


55 '39 


42-29 


45-36 


1871 


28-83 


36-06 


45-60 


42-15 


56-42 


47^5 


57-60 


38-96 


58-90 


55-io 


50-81 


4S -I 6 


1872 


38-44 


35-63 


40-20 


42-35 


40-61 


47-89 


49-50 


40-06 


60-76 


55'33 


43-95 


4S-5o 


1873 


43-09 


35-79 
36-17 


49-50 


42-23 
42-62 


56-11 


47-48 
47-94 


39-30 


40-58 
40-52 


40-30 


55-63 
54-82 


48-04 


45-4I 
45-55 


1874 


39-37 




37-20 




80-91 




46-80 




56-11 




44-32 




1875 


56-42 


36-33 


40-80 


42-34 


62-93 


49-58 


51-00 


40-83 


81-84 


54-89 


61-10 


45-49 


1876 


45-26 


37'29 


50-70 


42-27 


83-39 


50-22 


78-30 


41-31 


69-13 


56-17 


70-42 


46-23 


1877 


4371 


37-65 


72-00 


42-65 


88-35 


5173 


57-30 


43-oo 


43-09 


56-76 


55-68 


47-33 


1878 


49-91 


37-91 

38-41 


61-20 


43 '93 
44-65 


42-78 


53'32 
52-88 


68-70 


43-62 
44 -66 


62-93 


56-16 
56-45 


57-21 


47-69 
48-09 


1879 


25-73 




44-10 




59-52 




84-60 




75-95 




56-74 




1880 


62-31 


37-9I 


45-00 


44-63 


104-47 


53-iS 


111-30 


46-26 


75-95 


57-23 


68-33 


48-44 


1881 


59-21 


38-85 


51-60 


44-64 


64-17 


55"i2 


81-90 


4876 


60-76 


57"95 


68-56 


49-20 


1882 


62-00 


39-60 


56-70 


44-90 


76-57 


55H6 


72 90 


49-99 


79-67 


58-05 


73-45 


49-92 


1883 


43-40 


40-40 
40-50 


57-30 


45-32 
4573 


93-93 


56-21 

57-5I 


71-40 


50-81 
5I-52 


79-67 


58-82 
59'54 


68-84 


5076 

5f38 


1884 


52-70 




73-80 




76-57 




57-00 




88-35 




68-04 




1885 


52-70 


40-91 


59-70 


46-67 


54-87 


58-I5 


67-50 


5 I 7o 


69-13 


60-50 


66-51 


5I-94 


1886 


38-75 


41-29 

41-21 


52-50 


47-09 
47-26 


69-44 


58-04 
58-40 


61-80 


52-21 
52-51 


64-48 


6078 
60-90 


59-18 


52-41 
52-62 


1887 



VOL. XXXV. PART 3. 



2 X 



2&2 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXX.— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 
Wind Force, Accumulated Quantities from Month to Month. 



Year. 


January. 


February. 


March. 


Ap 


11. 


May. 


June. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


1856 


37-82 




101-62 




152-77 




182-17 




212-24 




269-24 




1857 


38-75 




88-31 




146-59 




181-99 




206-48 




225-98 




1858 


73-16 


38-28 


123-56 


94-96 


182-15 


149-68 


225-65 


182-08 


267-19 


209-36 


307-99 


247-61 


1859 


91-45 


49-91 

60-30 


166-21 


104-50 
"9-93 


265-10 


160-51 
186-66 


335-00 


196-61 
231-21 


361-04 


228 '64 
261 75 


410-84 


26774 
303-53 


1860 


55-18 




122-75 




183-20 




229-70 




273-72 




312-12 




1861 


41-23 


59 "27 


103-39 


120 '49 


185-23 


185-96 


219-13 


230-90 


255-71 


264-13 


282-11 


305-23 


1862 


52-08 


56-27 


90-16 


117-64 


132-32 


185-84 


179-42 


228-94 


218-79 


262-73 


268-89 


301 -38 


1863 


61-38 


55 - 67 


114-58 


113-72 


162-32 


178-20 


218-42 


221-87 


253-76 


256-46 


285-26 


29675 


1864 


4774 


56-38 
55'42 


85-73 


113-82 
110-70 


131-30 


176-21 
171-22 


161-90 


22 1 -44 
214-82 


196-93 


256-12 
249 '54 


240-73 


295'31 
289-24 


1865 


61-07 




96-91 




147-13 




183-73 




229-61 




262-91 




1866 


67-58 


55 '99 


120-50 


109-33 


166-38 


168-82 


212-58 


211 72 


245-13 


247 '56 


270-93 


286 62 


1867 


44-33 


57'o4 


103-97 


110-34 


154-50 


168-59 


209-70 


21179 


250-31 


247 '33 


279-71 


28518 


1868 


59-52 


55-98 


152-61 


109-81 


218-64 


167-42 


265-44 


2ii'62 


311-63 


247 '58 


359-03 


28473 


1869 


56-73 


56-25 
56-29 


114-13 


113-10 
113-18 


158-46 


171-36 
170-44 


200-46 


21576 
214-67 


245-10 


252'5I 

251-98 


277-50 


290-45 
289-52 


1870 


32-24 




79-84 




120-45 




170-25 




215-82 




249-42 




1871 


42-16 


54-68 


101-52 


110-95 


159-49 


167-10 


200-29 


21 1 70 


235-01 


249-56 


267-11 


286-84 


1872 


66-03 


S3'90 


122-00 


110-36 


177-80 


166 62 


242-00 


210-98 


291-29 


248-64 


326-69 


285-60 


1873 


63-86 


54-62 


101-94 


111-05 


142-24 


167-29 


186-34 


212-82 


224-47 


251-17 


264-07 


288-03 


1874 


69-44 


55-13 

55-88 


105-84 


110-54 
110-29 


177-14 


165-89 
166-48 


226-94 


211-34 
2I2'l6 


267-86 


249-68 
25063 


313-16 


28670 
288-08 


1875 


54-25 




93-17 




138-43 




169-03 




204-68 




237-68 




1876 


73-47 


55-8o 


126-83 


109-44 


220-14 


165-08 


279-24 


2I0'00 


324-50 


248'33 


376-10 


285-56 


1877 


93-31 


56-64 


176-47 


110-26 


244-67 


16770 


326-57 


213-30 


400-04 


251-96 


460-94 


289-87 


1878 


59-52 


58-31 


107-40 


113-28 


182-42 


171-21 


230-12 


218-46 


286-23 


25870 


324-33 


297-66 


1879 


53-94 


58-36 
58-18 


100-98 


113-02 
112-52 


193-36 


171-69 
172-60 


246-46 


218-96 
220'II 


298-54 


259-89 
261-51 


339 04 


298-81 
300-50 


1880 


56-42 




143-42 




186-51 




248-31 




310-93 




356-53 




1881 


39-37 


58-11 


93-69 


1 13 76 


182-66 


173-16 


238-76 


221-24 


297-66 


263-49 


357-96 


302-74 


1882 


90-52 


57 '39 


169-76 


112-99 


282-91 


I73-52 


357-01 


221-91 


407-54 


264-80 


458-84 


304-86 


1883 


90-21 


58-6i 


201-93 


115-08 


294-62 


I77-S6 


359-42 


226-90 


437-85 


270-07 


485-25 


3">'55 


1884 


121-52 


S9'74 
61-87 


214-03 


118-18 
121-49 


285-95 


181 74 
I85-34 


330-05 


23I-64 
235"04 


395-46 


276-07 
280-19 


443-16 


31679 
321-16 


1885 


72-85 




148-45 




238-04 




307-94 




377-07 




426-27 




1886 


93-69 


62-24 


135-97 


122-39 


216-28 


187-10 


294-86 


237 '47 


359-34 


283-42 


425-04 


324 '66 


1887 


85-56 


63-25 
63'95 


152-20 


122-83 
12375 


208-31 


188-04 
188-68 


267-11 


239-32 
240-20 


328-49 


285-87 
287-21 


369-59 


327-90 
329-21 



MEAN SCOTTISH METEOROLOGY, 



263 



Table XXX. continued,— SCOTTISH COUNTRY AND TOWN STATIONS, METEOROLOGY OF. 

Wind Force, Accumulated Quantities from Month to Month. 



July. 


August. 


September. 


October. 


November. 


December. 




























Year 

repeated. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


Obsd. 


Successive 
Means. 


310-78 




342-09 




392-79 




420-07 


*- 


449-17 




507-14 




1856 


274-03 




306-27 




347-67 




387-66 




420-66 




492-58 




1857 


342-40 


292 "40 


373-09 


324-18 


423-49 


370-23 


482-39 


403-87 


515-09 


434'92 


570-89 


499 "86 


1858 


455-48 


309-07 
345 "69 


504-46 


340-48 
38I-49 


558-46 


387-98 
430-61 


608-99 


430-04 
47479 


648-29 


461 '64 
508-31 


700-06 


523-54 
567-67 


1859 


339-09 




374-74 




407-44 




479-98 




512-68 




555-15 




1860 


325-82 


344'3S 


385-34 


380-12 


426-74 


425-96 


466-42 


475 "8 1 


537-22 


5°9' I 7 


574-42 


565-16 


1861 


323-45 


341 '27 


348-87 


381-00 


376-47 


426-10 


440-64 


474 '25 


464-64 


5i3'85 


531-29 


56671 


1862 


317-19 


33 8 '73 


352-53 


376-42 


403-23 


419-02 


448-49 


469 -46 


489-59 


506-83 


563-68 


561-66 


1863 


76-38 


336-04 
329-40 


310-17 


373 '43 
366-39 


355-17 


417-04 
410-16 


393-92 


466-83 
45873 


427-82 


504-67 
496-I3 


468-43 


561 -90 
55I-52 


1864 


293-29 




320-57 




358-07 




411-70 




443-50 




521-00 




1865 


298-83 


325-80 


334-79 


361-82 


375-59 


404-96 


408-45 


454 '°3 


461-85 


490-87 


517-65 


54 8 -47 


1866 


311-95 


323'34 


342-02 


359'36 


385-82 


402 -29 


428-29 


449-89 


459-19 


488-24 


508-79 


S45-67 


1867 


388-17 


322-39 


437-77 


357-9I 


474-07 


400-91 


524-91 


448-08 


566-01 


485-80 


618-40 


542-58 


1868 


317-18 


327-46 
326-72 


353-14 


364-06 
363-28 


410-14 


406 '54 
406-80 


460-36 


453 '99 
4S4"4S 


517-96 


491-97 
493'84 


575-31 


548-4I 
550-3S 


1869 


281-97 




308-01 




341-91 




358-41 




419-61 




459-29 




1870 


301-52 


3 2 3'73 


340-58 


359'59 


37178 


402-47 


415-80 


450-04 


456-60 


488-88 


507-44 


S44'27 


1871 


362-34 


322'34 


391-17 


35 8 '40 


436-77 


400-55 


493-19 


447-90 


550-79 


486-86 


609-69 


54I-96 


1872 


297-86 


324-70 


336-30 


360-33 


376-50 


402-68 


417-11 


45o-57 


466-61 


490-63 


527-37 


545 '96 


1873 


348-19 


323-21 
324-51 


391-28 


359'oo 
360-68 


440-78 


401 -23 
403'30 


496-89 


44871 
451-24 


536-19 


489-29 
49176 


576-49 


544-92 
546-58 


1874 


271-47 




310-84 




348-04 




428-95 




475-75 




531-86 




1875 


440-27 


321-86 


496-69 


358-I9 


537-49 


400-53 


600-42 


450-11 


651-42 


490-94 


733-26 


545 '83 


1876 


518-29 


327-5° 


563-55 


364'79 


614-25 


407-06 


697-64 


457-28 


775-94 


498-S9 


845-07 


554'76 


1877 


363-70 


336-i8 


407-41 


373 '83 


479-41 


416-48 


567-76 


468-21 


625-06 


511-21 


668-15 


567 '97 


1878 


401-04 


337 '37 
340-04 


450-95 


375'28 
378'45 


512-15 


419-21 
423-10 


554-93 


472-53 
475 '9 8 


623-63 


516-15 
520-64 


686-56 


572-3I 
577-09 


1879 


390-94 




416-67 




460-77 




520-29 




604-89 




680-84 




1880 


420-89 


342-07 


483-20 


379-98 


528-20 


424-61 


632-67 


477-76 


743-97 


524-02 


819-92 


581-25 


1881 


505-03 


345'iQ 


564-24 


383'95 


615-84 


428-59 


680-01 


48371 


761-91 


532-47 


822-67 


590-42 


1882 


533-61 


35i-oi 


595-61 


390-61 


652-31 


435-5I 


728-88 


490-97 


801-78 


540-96 


881-45 


599' 01 


1883 


480-36 


357-53 
36178 


523-76 


397-93 
402-28 


581-06 


443 - 25 
448-01 


674-99 


499-46 
505-52 


746-39 


550-27 
557-04 


826-06 


609-09 
616-58 


1884 


46S-12 




520-82 




594-62 




671-19 




728-19 




816-54 




1885 


494-17 


365'32 


546-87 


406-23 


606-57 


452-9° 


661-44 


5ii-o5 


728-94 


562-75 


798-07 


623-25 


1886 


423-22 


369-48 
37i'i7 


461-97 


410-77 
412-38 


514-47 


457 '86 
459'64 


583-91 


5i5'9o 
518-03 


64571 


568-11 
570-53 


710-19 


628-89 
63i'43 


18S7 



264 



PROFESSOR C. PIAZZI SMYTH ON 



Table XXXI.— MONTHLY ELEMENTS OF ALL SCOTTISH METEOROLOGY, REDUCED TO 
ONE CENTRAL GEOGRAPHICAL POINT, VIZ.: 

Latitude = 56° 30' N.; Longitude = 3° 40' W.; Height = 256 Feet; Distance from General Sea-Coast, 
Eastward, 40; West, 90; North, 120; South, 120 Miles; — and for the Mean Epoch of the 
Years 1856 to 1887 inclusive. 



Table. 



Old 
Tables. 

1 
2 

3 
4 

5 
6 



10 

11 
12 
13 

14 

15 



16 

17 
18 



19 
20 



New 

Tables. 

21 

22 

23 

24 
25 

26 



26 a 

27 

28 

29 
30 



Subject. 



Barometric Mean Pressure, 
Monthly Range, 



Temperature, Mean in Shade, 
Daily Range, Mean in Shade, 

Mean of Max. Temperature by Day, 
Mean of Min. Temperature at Night, 

Humidity, Relative, computed from the 

Bulb Thermometer 

Depression of Wet Bulb below Dry, 
Depression of Dew Point, 
Elastic Force of Vapour, 
Grains of Moisture in cubic foot of Air, 
Grains further required to saturate 
cubic foot of air, .... 

Rain, Number of Days on which it fell, 
Monthly Depth of Rainfall, . 
Annual Depth of Rainfall, 

Wind, Mean Force of, . 



Wind, Direction of, North, 
,, ,, East, 

South, 
„ „ West, 



Wet 



that 



Sunshine, No. of Hours of, per Month, . 
,, ,, per Year, . 



Cloud, Mean Amount of, 
Lightning, 



Auroras, 



Mean Maximum Temperature in Shade, 
Mean Minimum Temperature in Shade, 

Accumulated Rainfall, Depth, 

Plant-Growth Temperature, .... 
Accumulations of each kind of Plant-Growth 

Temperature, ...... 

Accumulations made good of Plant-Growth 

Temperature, 

Preparatory only for 27 and 28, . 
Frost, Exposed in each month, . 
Fire, Exposed in each month, . . . . 

Wind-force per month, . 

Wind-force, Accumulated Quantities, . 






Terms. 



Inches, 
Inches, 

° Fahr., . 
°Fahr., . 

° Fahr., Expd. Bl. B. 
° Fahr., Expd. Bl. B. ; 

Sat. =100, . 

°Fahr., . 

"Fahr., . 

Inch, 

Grs., . . . . 

Grs., . 



Days, 

Inches, 

Inches, 

Lbs. Av. on Sq. Foot, 

Days, 
Days, 
Days, 
Days, 

Hours, 
Hours, 

Hemisphere = 10, 

Days, 

Stations, . 
Days x Stations, 

Nights, 
Stations, . 
Nights x Stations, 



° Fahr., . 
° Fahr., . 

Inches, 

Above 42°, or + 
Above 42°, or + 
Below 42°, or - 

Below 42°, or - 



Below 32°, or - 
Above 32°, or + 



lbs. pressure x into days 
( The above from be- 
( ginning of year. 



Jan. 



487 
28-3 



1-5 
3-5 

0-19 
2-20 

0-40 



17 
4-03 



2-06 

4 

5 

9 

11 

63 

67 

1-5 

12 

18-0 

2-0 

8 

16-0 



41-5 
32-5 

4-03 

-155 
-155 

-155 



-17-8 
+ 34-0 

63 '95 
63-95 



Feb. 



29-831 
1-480 

38-4 
9-9 

56-1 
29-2 



1-5 
3-6 

0-20 
2-30 

0-40 



15 
3-14 



2-11 

4 

5 

8 

10 

85 

6-5 
1-1 



1-9 
11 

20-9 



43-4 
33-5 

7-17 

-101 

-257 



-256 



-16-0 
+ 44-2 

59-80 
123-75 



March. 



29-833 
1-446 

39-5 
11-8 

64-0 

29-4 



1-8 
4-0 
0-21 
2-40 

0-40 



15 
2-83 



2-09 

6 

6 

6 

10 

124 



6-4 

1-2 

6 

7-2 

2-0 
9 

180 



45-4 
33-7 

10-00 

- 77 
-339 
+ 6 

-334 



-15-5 

+ 54-4 

64-93 

188-68 



April. 



29-888 
1-264 

44-2 
14-1 

73-7 
32-3 



83 

2-0 
4-4 
0-24 
2-80 

0-50 



12 

2-24 



1-72 

6 

8 
7 
8 

162 

6-3 

1-2 

13 

15-6 

1-8 

8 

14-4 



51-3 
371 

12-24 

+ 66 
-341 

+ 74 

-267 



-11-0 
+ 64-7 

51-52 
240-20 



May. 



29-930 
1-076 



15-4 

81-7 
35-9 



30 
6-0 
0-28 
3-10 

0-90 



13 

2-27 



1-52 

6 

8 
7 
9 

201 

6-2 

1-7 

19 

32-3 

1-0 

2 

2-0 



56-5 
41-1 

14-51 

+211 
-341 

+285 

- 57 



- 8-1 
+72-1 

47-01 

287-21 



June. 



29-928 
0-919 

54-8 
15-6 

90-1 
41-9 

81 

3 
5-9 
0-35 
3-90 

1-00 

13 
2-53 



1-40 

5 

6 

8 

10 

217 

6-2 

2-2 

26 

57-2 

0-1 



0-0 



62-6 
47-0 

17-04 

+384 
-341 
+ 668 

+327 



- 17 
+ 79-7 

42-00 
329-21 



MEAN SCOTTISH METEOROLOGY. 



265 



Table XXXI. continued.— MONTHLY ELEMENTS OF ALL SCOTTISH METEOEOLOGY, REDUCED 
TO ONE CENTRAL GEOGRAPHICAL POINT, VIZ.: 

Latitude = 56° 30' N; Longitude = 3° 40' W.; Height = 256 Feet; Distance from General Sea-Coast, 
Eastward, 40; West, 90; North, 120; South, 120 Miles, — and for the Mean Epoch op the 
Years 1856 to 1887 inclusive. 



Table. 



Old 

Tables. 
1 
2 

3 

4 



10 

11 
12 
13 
14 

15 



16 

17 
18 



19 
20 



New 

Tibles. 

21 

22 

23 

24 
25 

26 

26a 
27 

28 

29 
30 



Subject. 



Barometric Mean Pressure, 
Monthly Range, 



Temperature, Mean in Shade, 
Daily Range, Mean in Shade, 

Mean of Max. Temperature by Day, 
Mean of Min. Temperature by Night, 



Humidity, Relative, computed from the Wet ) 
Bulb Thermometer, . . . . ) 

Depression of Wet Bulb below Dry, 
Depression of Dew Point, 
Elastic Force of Vapour, . 
Grains of Moisture in Cubic Foot of Air. 
Grains further required to saturate 
cubic foot of air, .... 



that 



Rain, No. of Days on which it fell, 
Monthly Depth of Rainfall, . 
Annual Depth of Rainfall, 



Wind, Mean Force of, 



Wind, Direction of, North, . 
„ ,, East. 

South, . 

West, . 

Sunshine, No. of Hours of, per Month, 
„ „ per Year, 

Cloud. Mean Amount of, 

Lightning 



Auroras, 



Mean Maximum Temperature in Shade, 
Mean Minimum Temperature in Shade, 

Accumulated Rainfall, Depth, .... 

Plant-Growth Temperature, 

Accumulations of each kind of Plant-Growth ) 

Temperature, J 

Accumulations made good of Plant-Growth ) 

Temperature, J 

Preparatory only for Tables 27 and 28, . 

Frost, Exposed in each Month, .... 

Fire, Exposed in each Month, .... 

Wind-Force per Month 

Wind-force, Accumulated Quantities, . 



Terms. 



Inches, 
Inches, 

° Fahr., . 
"Fahr., . 

° Fahr., Exp. Blk. B., 
° Fahr., Exp. Blk. B., 

Sat. =100, . 

°Fahr., 

"Fahr., 

Inch, 

Grs., .... 

Grs., .... 

Days, 

Inches, 

Inches, 

Lbs. Av. on Sq. Foot, 

Days, 
Days, 
Days, 
Days, 

Hours, 
Hours, 

Hemisphere = 10, 

Days, 

Stations, . 
Days x Stations, 

Nights, 
Stations, . 
Nights x Stations, 



Fahr., . 
° Fahr., . 

Inches, 

Above 42°, or + 
Above 42°, or + 
Below 42°, or - 

Below and above 42°, 



Below 32°. or - 
Above 32°, or + 

lbs. pressure x into days 
( The above from be- 
( ginning of year. 



July. 



29-879 
0-897 

57-4 
15-0 

91-4 
44-9 

82 

3-0 
5-8 
0-38 
4-30 

1-00 

15 
3 Tl 



1-35 

5 

5 

8 

12 

211 

6-5 

2-5 

29 

72-5 

0-3 



0-0 



64-9 
50-0 

20-15 

+ 478 
- 341 
+1146 

+ 805 



+ 2-1 
+ 80-6 

4196 
371-17 



Aug. 



29-861 
0-974 

56-8 
14-5 

88-9 
44-2 

84 

2-5 
4-8 
0-39 
4-40 

0-80 

15 
3-40 



5 

5 

8 

11 

182 

6-5 

1-8 

25 

45-0 

1-5 

5 

7-5 



64-0 
49-6 

23-55 

+ 457 
- 341 
+ 1604 

+1262 



+ 0-8 
+78-8 

41-21 
412-38 



Sept. 



29-833 
1-188 

52-8 
13-6 

81-9 
40-5 



2-0 
4-0 
0-35 
3-90 

0-60 



16 

3-74 



1-58 

5 

5 

8 

11 

145 

6-3 

1-4 

17 

23-8 

2 1 

8 

16-8 



59-6 
46-0 

27-29 

+ 323 
- 341 

+ 1926 

+ 1585 



- 3-3 

+ 71-8 

47-26 
459-64 



Oct. 



29-814 
1-466 

46-6 
11-9 

68-4 
35-3 



1-8 
3-8 
0-27 
3-20 

0-40 

16 
4-03 



5 

6 

8 

10 

110 

6-4 

1-5 

13 

19-5 

2-0 

11 

22-0 



52-5 
40-6 

31-32 

+ 142 
- 341 

+2068 

+ 1727 



- 9-9 

+59-8 

58-40 
518-03 



29-817 
1-539 

40-4 
10-3 

55-4 
30-2 



1-5 
3-4 
0-22 
2-60 

0-40 



16 
3-73 



1-75 

6 

5 

7 

10 

77 

6-4 

1-5 

10 

15-0 

2-1 

9 

18-9 



45-6 
35-3 

35-05 

- 48 

- 396 

+2075 

+1679 



-14-6 
+ 43-1 

52-51 
570-53 



29-779 
1-563 

37-7 
9-5 

47-6 

28-4 



1-2 
3-0 
0-20 
2-20 

0-30 



16 

4-07 



1-96 

6 

4 

8 

11 

60 

6-5 

1-5 

9 

13-5 

2-0 

7 

14-0 



42-5 
33-0 

39-12 

- 133 

- 533 
+2079 
+ 1546 



-18-0 
-+-30-9 

60-90 
631-43 



Mean of 
Year. 



29-846 
1-290 

46-2 
12-5 

707 
35-1 

85 

2-1 
4-5 
0-26 
3-10 

0-50 

15 

3-26 

39-12 

1-73 

5 

6 

7 

10 

136 
1637 

6-4 

1-6 

15 

24-0 

1-6 

7 

11-2 



52-5 
39-9 



+ 129 



- 9-4 

+ 59-5 

52-62 



VOL. XXXV. PART 3. 



2 Y 



>y. Soc. EdirL 



.O.ED. SCOTTISH METEOROLOGY, I*s6-W]. 



Vol. XXXV 



PLATE 1. 



s 



Mr /%So /fft /*8~° 

(T ' y * 9 O / 2 34-S^P-^9Q/ * 3 ^S f ' T » 9 O ' 2 3 * f * 7 * ? 




A. Ritchie f Sort, Photo- Lith. 



Roy. Soc. E din. 



:.O.ED. SCOTTISH METEOROLOGY, 1856- W/. 



Vol. XXXV. 



PLATE 2. 



\.r of 



Vtsr /86o /tyo /ssa 

6 7 8 9 O / 2-34f67*?0' 2-34.S'6 7BfO/234.f6787 




CP. S. obs. §■ del. 



Roy. Soc. Edin. 



.O.ED. SCOTTISH METEOROLOGY, /8S6 -ISB7. 



Vol. XXXV 



PLATE 3. 



XT Of- 

St ss 



I9SST /860 #7* tS86 

47890 / 2$*£67*?O'2*tf47*?0/244 J~* 7 8? 




0. ED. SCOTTISH METEOROLOGY, 1856-188]. 



Vol. XXXV 



PLATE 4. 



/$&■ /$6o /8yo /eeo - ^-— - 




C.P. S. obs. §■ del. 



'*?'& 






Roy. Soc. E din. 



,O.ED. SCOTTISH METEOROLOGY, /tf£/n?. 



Vol. XXXV 



PLATE 5. 



a 


r <*- 


/W J$6b 1ty0 /B%o 


Is. fc= 


6 Z* 9 O / 2 J 4. &€ y * 9 O / 2 2 4$~f ? * 9 O ' 1 3 4~& * T * 9 


U 


•tf — 


'Ml £^ 




^I^FW 








'i 


o — 


1 *^fll iflk' 


,^H H^ 




^fcA 




6 


'0 — 


*jfj Nhw il SL 


^^^fc^^M W%%Z>'ss. 


' 




1 


'••''lli 


£A»W?-e'$ /V^ 


-»v Grctcfis oy 


« <5W SP<?7 


'$, Ctm.t* ffl ~ AT<.*^ <3Z:><yvo^oyy. 




•* 






10L 












7 






m 








I 


© 




•5" 

•5" 






















•& 1 






*?l 














'4 
•3 


•V 1 






iSt 














•2 


:l! 1 






!p fl 


Mi 






1 







•/ 


:?i 1 






^»! > 








II 




>7 


•<9 

7 


'?• I 






In * i? 








III 


$ 1 

?! 1 






■in 




■ w i^H\ iOiM 


1 




•fr 


;: 1 


iC 


ji ' 


1 Bi^tl ' ■■I vGSrv 


y%3H IB 1 


1 1 i£A\/Jll 


■J 




7 


•i«t • I 










II 






>< 


!*! I 






vto& 


nil II 1 




II 






tf 


•IJ' 1 






V/riT?^ 






| 






" •"*! 1 






\CJjr 


III II 1 










•4- 


3 ! 1 

»C ■ 1 






111 M I 










•3 


:v 1 


//*W II ill till K5r 














•a 


|S! 1 




TiOi J Ml 












3 


'/ 




A 1 












( 


•0 


.Vi 


i fill III 














1 








III 1 1 








'8 

■7 












■ II Ml 




4 


ft 














-5 


i • 










W^?a IH^Bl 




<£' 














'k 


:$ 


iV I 11 i/flf i^)l 






i\D/ 1 






•3 


| 
















•2 


§ 




iCv/ 










c 


•0 










■ 
















■ 








'9 
















•S 


















7 


















•6' 
-3 


CWf 


C^/fif 7is^ 


E£ 2. 










(i 


/4fe*n iM 


^ a?e 7e»y6. -|- 


Me** AIak.o 


c $heJe !«->»/>. 


-tvtfes/t m 


EUcP lull 


Zy day. 


€ ' Y tf/ 


^/^ 


C> / 3 3 4.,; 


r<r r % ? c 


) / 2 3 4- *.' 


?* ? * 9 


O / 2 3 4 c' 


I s - <r^ r^ 


_£ 


5.^: 


/to> /8 


-<rb 


/ 8- 


^ 


/I 


ffro 





Ut lie f Son, Photo- litk.. 



C P. S. oos. §- del. 



Roy. Soc. Ed in. 



D. ED. SCOTTISH METEOROLOGY, 1856-/88/. 



Vol. XXXV 



PLATE 6. 




4! <>h 



<> 7 8 f / 234-S~678?0/ I 3 4-S 6 ? 8 9 O / 7. 3, 4 S 6 / 8 ? 
'8Sf /860 /8?0 /SSO 



'■tcie. f Son, Photo- Luh.. 



C.P.S. ois. & del. 



Roy. Soc. E d in. 



Vol. XXXV. 



).ED. SCOTTISH METEOROLOGY, /8S6-/881p LAT£ 7 , 



* 



WS? /86o /8po /880 

67 8?Q/l3 4-S'67 8?d'Z$4'*r67S?0/'L54'S678 9 




C P. S. ois. §■ del 



Roy. Soc. Edin. 



0. ED. SCOTTISH METEOROLOGY, J856-/8SJ. 



Vol. XXXV 



PLATE 8. 



S. r 



l/SST /S60 /8JQ /$8o 




iSchwat*'* 



frou-fii oj. SUN- SPOTS, co*ihtKu*ct as- K<m Ol^vv^f-ovy 





TABL£ 



//, JO/tyf cf. 



7VorfL \+ 



\taf- 




TABLE /2» 3> A y* '/ 



EAST n"W. 




TABLE. I 



3> J) ays 0/ 



South ^fnd 




TABU i%*z* y < </. /{/£$T 



H"*V« 



6 7 8 ? / 134-^^7^90/ Z34-S678?0/z34-567 8? 
gcr /86p /tm /a so 

f Son, Photo- Utk- C.P.S. obs &■ del 



Roy. Soc. Edin. 



0. ED. SCOTTISH METEOROLOGY, 1856-1887 



Vol .XXXV 



PLATE 9. 





Table /6. Tercenhye. cfClotlb. 






* 7 8 ? O ' 2 3 4- $ 6 7 8 ?0/Z34-S6?8?0/2.a4-5't7 8<? 
/ssi- /86o. /87c. /88Q. 



Wz j- Son, Photo- lith. 



C.P. S. oi>s. §■ del. 



ns. Roy. Soc. Edin. 



Vol. XXXV. 



10. ED. SCOTTISH METEOROLOGY, I856-I8S? 



PLATE 10. 



Year oA 



{>sx> fS6o /8?o /880 

67 8 ? Q / i~ 3 i* 5T 6 j z f Q / Z34.S6?8fQ/ Z 3 4 5 * 7 8 9 



'ear of 

oh. ■+ 




«7 8 fO/ * 3 4- S 6 7 8 t O ' 7. 3 dn S * 7*10' 23 4 f 6 7 8 f 

l&W /S60 /8?o I880 



Ritchie $ Son. Photo -Ink. 



C.P.S. ois & del 



Trans. Roy Soc. Edin. 



Vol XXXV 
PLATE 11. 



R.O.ED. SCOTTISH METEOROLOGY, /856-/ZSJ. 



Year of- 

ah- ~ 



i&fo J&?c /&#0 , 

6?»9Q/Z34. ft y s 9 / * 3 a S'i' tJLZSLLJJLJt £. * r * £ 




.2£l=J (B(To tS?o /8-&0 

A-UcMe $ Sort, Photo -IWt. 



C.P.S'.obs. §■ del. 



rans. Roy. Soc. Edin. 



R.O.ED. SCOTTISH METEOROLOGY, 1856-188]. 



Vol XXXV 



PLATE 12. 




C.P.S. obs. f del. 



rans. Roy Soc. Edin. 



R.Q ED. SCOTTISH METEOROLOQY, 1856-182/. 



Vol. XXXV 



PLATE 13. 



Ytar o/- 
0iy = 



V8ST /86o /8?Q /880 

6 7 8 9 O ' Z34.S6y8?Q/2.3 A- S 6 7 X 9 O / % 3 4-5678? 




I. or of- 



itchie. f Son, Pboto-litft. 



& 7 9 ? O / 9. 3 4- S 6 7 Z f O / 7-34-S6 78?0' Z 3 4- S 6 ? Z f 



/860 



/s;o 



/880 



C.P.S. obs. §- d&L 



ans. Roy. Soc. Edin. 



R.O. ED. SCOTTISH METEOROLOGY, M6-/88J. 



Vol. XXXV 



PLATE 14. 



(8sr J*tc /sp m mo 

67&?O / i~34f'*7B?0/ I <3 4 ST 6 7 8 9 0/ 234-&67&9 




sPcA'VolZ*'* /fey* yroa^s oj. SUN '- >TOT% , fgnftHu^ a~f Kt.w 0Zs*.Y>a.t"OYy< 



TABi.E. 2/. TRMT", rHJI«^re/j/i»3 J-/**- Freezny Toivth* 




€ 7 8 f I 2 3 4- S- 6 ? 8 ? O I Z 3 4. 5" 6 7 8 ? / 2l 3 ^ S i 7 B 9 
IMS /86c /l/g /*#> 



"'■■JcAifi 4. j^, Photo -lith.. 



C.P.S. obs. §■ d&l. 



• 1 




MEAN SCOTTISH METEOROLOGY. , 267 

PAET III. 

Thirty-one Chronological Tables op Mean Scottish Meteorology, Month by 
Month, from 1856 to 1887 inclusive, — Explanations of. 

These Tables are derived by immense condensation from the bi-diurnal observations 
taken voluntarily and with remarkable assiduity, by the observers of the Scottish 
Meteorological Society, at 55 of their stations scattered over the whole country of 
Scotland (Highlands and Islands included) ; and computed by order at the Eoyal Observa- 
tory, Edinburgh, for the purposes of the Kegistrar-General of Births, Deaths, &c. in 
Scotland, for every month in every year from 1856 to 1887 inclusive. 

1. Historic Origin of the Data. 

When the Astronomer in charge of the Royal Observatory, Edinburgh, was first 
called on by Government in 1858 to begin his part in the above Meteorological calculations 
for the purposes above stated, he found a generally excellent system already organised, 
and worked for two years by the late Dr Stark, then the enthusiastic Secretary to the 
Scottish Meteorological Society, as well as a scientific and responsible officer in the depart- 
ment of the Registrar General for Scotland. 

Continuing that system, the ordinary instrumental corrections were carefully applied 
at the Observatory, and monthly means, collected from the bi-diurnal observations of all 
the stations, were exhibited and printed, first for each station by itself, giving all its 
individual characteristics untouched; and next for the mean of all the 55 stations ; or 
for something very like the one geographical and physical centre of the whole Caledonian 
country. For, such an extensive condensation of the records of many instruments and 
many observers would, it was hoped, possess a certain solidity of accuracy ; and justify 
confidence in it to a greater extent than any single observer, either in town or country, 
could ever expect to attain to. 

But there was still no opportunity of ascertaining for any month in any year, how far 
that season might be an extraordinary one, as touching any, much more all, the usual 
meteorological items of study. The historical element as to annual recurrences, agreements 
or disagreements, and cyclical rises and falls of many years, was then in fact entirely 
wanting ; and could only be expected to be supplied by continuous observation united 
with undeviating registration of them through many years. In a manner however 
quite suitable for a Government Observatory to engage in, and become responsible for. 
To supply this confessed want therefore, the Astronomer specially applied himself; and 
entered each month's means for the collected country in ledgers, as the years went by, in 
the form best adapted for successive chronological digests being taken, for every succeed- 
ing accumulation of years from the beginning of the activities of the Scottish Meteoro- 
logical Society, down to the latest passing period. 

At first, from the frequently very great differences of the calendar months of one year, 
from those of another, even when the Mean of all the stations, or of the whole country, 
was concerned, these chronological means used to vary rather violently from each other. 



268 



PROFESSOR C. PIAZZI SMYTH ON 



But the differences were always decreasing, so that after 16 years had gone by, or in 
1871, I thought it useful for the public to print all those annual returns in the 13th 
volume of the Edinburgh Astronomical Observations, as a contribution to the successive 
time-features of the climate of the whole of Scotland. 

So quickly however has time gone on since then, that now 16 more years have been 
tabulated, and the final results are now for 32 years ; — giving thereby so great, though 
still not perfect, assurance of the limits of the surprises which Nature may have in store 
for this people in future years, — that if the first list was positively worth printing, the 
second must be far more so ; and has now even become necessary for the prompt refer- 
ences and methodical conclusions required for the Registrar General's work, as that great 
task of his still goes on, perpetually functioning simultaneously with the life and growth 
of the nation, and following in its mighty footsteps without a moment's intermission. 

On this second occasion, however, of preparing for printing, besides the 21 Tables of 
which the old series consisted, taking up all the more ordinary, and orthodox meteoro- 
logical points, I have added 10 new Tables to represent the. answers of observation to 
certain new requirements of scientific theory ; and shall proceed therefore to describe some 
of their contents and bearing at rather more length than the others, after duly recording 
that the chief labour and merit of preparing the 21 old Tables up to the year 1880, out 
of the millions of figures concerned therein, were mainly due to the late Mr Alexander 
Wallace, M.A., then First Assistant Astronomer in the Royal Observatory, Edinburgh. 
While similar merit is now also most eminently due to Mr Thomas Heath, B.A., of T.C.D., 
for continuing the old Tables from 1880 to the present year, and preparing the new Tables 
for the whole period from 1856 to the end of 1887. 

In September of that latter year, the 55 stations, carefully chosen for the Registrar 
General, by Mr Alexander Buchan, the present able Secretary of the Scottish Meteoro- 
logical Society, were distributed as follows through the 8 Registration Districts of the 
country, including islands as well as mainland. 

1. In the Northern, ....... 6 Stations. 

2. In the North- Western, 

3. In the North-Eastern, 

4. In the East Midland, 

5. In the West Midland, 

6. In the South- Western, 

7. In the South-Eastern, 

8. In the Southern, 

Total for all Scotland, 
and have for their Mean or Central point, Latitude 



Longitude 



6 

6 
10 

5 

5 
12 

5 

55 Stations. 

= 56° 30' N. 
= 3° 40' W. 
= 256 feet.* 



uud Height above Sea-Level 

* The above given latitude and longitude are nearly those of "the fair city of Perth"; but the height above sea- 
level is nearly double, depending on the mountains North and West thereof, chiefly. Sea-distance from general Sea- 
bowever remaining untouched, viz., Eastward, 40 ; Westward, 90 ; Northward, 120 ; and Southward, 120, miles. 



MEAN SCOTTISH METEOROLOGY. * 269 

This distribution, and these component numbers have not been always kept up exactly 
every year, notwithstanding the best efforts of the Scottish Meteorological Society so to 
do. But it is hoped they have always been preserved sufficiently near in Geographical 
harmony, to prevent the final Meteorological Means being seriously perverted. Wherefore 
the tables now presented, though sometimes of only 50, in place of 55, stations, may yet 
be regarded with approximation as equally distributed about the country's central position. 
While of the original 55, no less than 31 have continued identical in place throughout 
the period from at least 1867 to 1887: though with 19 changes of observers amongst 
them. 

2. Of the Old Tables newly continued to the Present Time. 

Table I. contains that necessary feature for all Meteorology, the mean monthly Baro- 
metric Pressure for each month, of each year, reduced according to order and precedent 
both to the temperature of 32° F., and to the sea level. The pressure is given in terms 
of British Inches, and amounts on the means of all the months and all the years to 
29*846. But with an evident annual cycle having a Max. in May and June = 29'929, 
and a rain, in December and January = 29 '7 6 4 inches. 

Table II. contains the Mean Monthly range of Barometric Pressure for all the stations, 
and amounts to 1*290 inch on the mean of everything. But with an annual cycle having 
a Max. in the beginning of January = 1*6/1, and a min. in July = 0*897 inch. 

Table III. is the biologically, botanically, and commercially important return of Mean 
Monthly Temperature of day and night, strictly in the shade, in degrees Fahrenheit, and 
amounts on the mean of all the months and all the years to 46° '2 F. But with an 
annual cycle having a Max. towards the end of July=57°"4, and a min. in January = 
37°*0 F. 

Table IV. is the almost equally important Mean daily range in each month of that 
shade-temperature; and amounts for a mean month of the whole year to 12°*5 F. Of 
which quantity, if half be first added to, and then subtracted from, the previous 46°*2, 
we shall have the highest and the lowest shade-temperatures in the cycle of a mean day 
of an annual average kind. See also the new Tables XXI. and XXII. But of such daily 
range there is an annual cycle ; whereof the Max. occurs in June = 15° '6, and the min. in 
the beginning of Januarys 9° '1 F. 

Table V. advances from Shaded to Exposed Temperatures, and by means of Black-bulb 
thermometers; of not always identical kinds, unfortunately; but for reasons stated on the 
back of the Observer's printed Schedules by the Secretary of the Society. This Table V. 
then gives the mean of all the daily readings for each month, or the mean of the highest 
points reached every day in each month, at all the stations, by their Black-bulb thermo- 
meters, fully exposed, nominally to the Sun, really to the sky, but by day alone. It is 
therefore a very peculiar kind of thermometer reading, and claims for Scotland an 
average, on the mean of all the days of all the months, of all the years and all the stations, 
so high as 70°*5 F.; including therefore without doubt some 18° of Solar radiation as well 

VOL. XXXV. PART 3. 2 Z 



•270 PROFESSOR C. PIAZZI SMYTH ON 

as the proper and acquired temperature in the shade of the atmosphere alone; which 
for the day half of the 24 hours is 46*2 + 6*2 = 52°4 F. But as to the annual cycle 
of these exposed Black-bulb day observations, its Max. occurs in July = 91 0, 4, and its 
min. in December = 47°'6 F. 

Table VI. gives the monthly means, of the cold extreme, or nightly observations of 
the same exposed Black-bulb thermometers, but now at night and the coldest part of 
each and every night. Establishing that such Mean, of exposed night temperature in 
Scotland, on the Mean as before of all the days of all the months of all the years and all 
the stations, is down so low as 35° - l F.; and includes about 5° of negative radiation 
effects from the open night sky. The shaded thermometers at night yielding on the 
whole no lower result than 46°'2 — 6° '2 = 40°'0. But as to the annual cycle of these Black- 
bulbs exposed by night, its Max. occurs in July = 44° - 9 and its min. between December 
and January = 28°*3 F. 

Table VII. sets forth the Mean monthly Humidity of the air, as measured by the 
depression of the wet, below the dry, bulb thermometer ; and computed according to Mr 
Glaisher's well known and most practical tables. It is then found to amount on the 
whole year and years to 85, where saturation = 100. While the number of grains of 
moisture in a cubic foot of the earth's gaseous atmosphere, or any other direct and positive 
expression of the amount of moisture has to be computed from that 85 of Humidity in 
combination with the shade-temperature, and Barometric pressure at the time and 
place. 

But these having been already given, for the one general mean of all the stations and 
all the years, as 46° *2 and 29*846 inches, there results very nearly 3'1 grains of watery 
vapour present in each cubic foot ; 0*5 grains further required to saturate the same bulk 
of air ; and 0*26 inch for the elastic force of vapour present in the air. The depression 
of the wet, below the dry, bulb being 2°*1 ; and the depression of the computed dew- 
point below the observed dry-bulb being 4° "5. 

Or showing the general climate of Scotland to be usually within half a grain of 
manifesting visible mist, instead of concealing it as invisible vapour, or water gas. But 
taking the mere " Humidity" return just as it stands, its annual cycle has its Max. in 
December=89, and its min. in May = 80. 

Table VIII. gives the mean number of days on which rain fell in every month ; and 
which, on the whole year and years amounts to the round number of 1 5 for every month. 
The annual cycle however shows itself in having a Max. = 17 in January, and a min. = 12 
in April. 

Table IX. represents the still more important feature of rain-fall, viz. its quantity, as 
measured by its depth when fallen. And while the table gives such depth for each 
month, it likewise gives the accumulated depth for each year, and the mean of the years, 
viz., 39*12 inches. A quantity however requiring immense alterations for individual 
localities, sometimes 4- and sometimes — , according to local position, as will be taken up 
in the second part of these Meteorological explanations. The annual cycle however 



MEAN SCOTTISH METEOROLOGY. 271 

of the single months, which has for its mean = 3'25, — has for its Max. in December 
= 4*07, and for its min. in April = 2*24 inches, British. 

Table X. seeks to record the mean amount of strength of wind in each month of each 
year; the mean of the whole being 1*73 lbs. constant pressure by night and by day on 
every square foot of surface; implying a velocity of over 18 miles an hour. A high return, 
showing perhaps the effect of proximity to the sea-board of most of the Scottish stations, 
however centrally in the country the mean of the whole may be located. Or perhaps it 
may indicate the difficulty of observing the true mean pressure of the air through the 
whole 24 hours, both independently of the impact of the rain drops, and the effect of 
momentary gusts on the feelings of humanity at the instant of observation. The annual 
cycle however comes out pretty evidently, with a Max. in February = 2*11, and a min. 
between July and August = 1'34 lbs. on the square foot. 

Table XL gives the mean monthly number of days on which winds of Northerly direc- 
tion blew, that is, all those entered North, and half of those entered N.-east ; with the 
same for those entered N.-west ; and amounting per mean month to 5. The annual 
cycle of these North winds is rather obscure, having something like two Max., one in 
April and one between November and December, each = 6 ; and two mm., one in January 
and February = 4, and another in August = 5. 

Table XII. gives similarly the number of days per month, on which Easterly winds 
blew, viz., 6. The annual cycle showing a Max. between April and May = 8, and a min. 
in December = 4. 

Table XIII. the number of days per month, on which Southerly winds blew, viz., 8. 
The annual cycle having a faint Max. = 9 in January, and a faint and short-lived min. 
in March = 6. 

Table XIV. the number of days per month on which Westerly winds blew, viz., 10. 
The annual cycle having its Max. in August = 12, and the min. in April = 8. 

Table XV. gives the mean number of hours of Sunshine in each month, amounting on 
a mean of all the months to 136; but varying between December and June from 60 to 
217, for astronomical as well as meteorological reasons. 

Table XVI. gives the estimated mean amount of Cloud per month, in decimals and 
tenths thereof, of the hemisphere; being, for a mean month = 6 "4. But varying between 
January and May between 67 and 6*2; or indicating a never very astronomical observ- 
ing climate. 

Tables XVII. and XVIII. both refer to Lightning. The former gives the mean 
number of days it is seen per average month, = 1 *6 ; and the latter records the number 
of stations reporting it = 1 5. 

The former kind of return arrives at its maximum in July, and = 2*5 ; while the 
latter kind reaches its maximum also in July, and = 29. 

Again the former kind attains its minimum in February, and=l"l ; while the latter 
has its minimum very near it, or in March, and then registers 6. 

So that multiplying the two kinds of return together, we have — 



272 PROFESSOR C. PIAZZI SMYTH ON 

Lightning max. in July = 72, and Lightning min., between February and March = 7. 

Tables XIX, and XX treat similarly of Aurora. The former giving the number of 
days on which it is seen per average month = 1 "6 ; and the latter recording the number 
of stations reporting it, viz., 7. 

The former table comes curiously and very decidedly to a double maximum ; viz. , 
in October = 2*1, and in February = 2*0. While the latter table confirms the former by 
coming also to a double maximum in the same months; viz., in October =11, and in 
February = 11. 

Again the former table comes to its minimum in June and July = 0*1; but partly 
owing to lengthened twilight days ; while the latter table comes also to its minimum in 
June and July, for probably the same reasons, and averages then per month less than 1. 

Wherefore combining the two kinds of return by multiplying into each other, we have 
the first maximum of Aurora in any whole winter season, occurring in October and 
registering 23 ; the second maximum in March = 22. And the one, or at least the utter 
minimum of the whole year between June and July, with a record of something less than 
1. While the comparative or necessary minimum between the two maxima, occurs in 
December, and reaches in its two components 2 x 7 = 14 on the whole return. 

The double annual maxima of Aurora are thus well marked out by the minima on 
either side of them, and are all the more interesting from being so absolutely opposed in 
date and character to the single annual maximum which Lightning obtains in the cycle of 
a year. That is to say, Lightning has its one annual maximum in July, just when Aurora, 
but under forced conditions, reaches its one most conspicuous minimum of the year. 

While at the same time the dates of Aurora reaching its two maxima for any winter 
season, are not corresponded to inversely by both of those being dates for Lightning falling 
to a minimum ; though the Spring maximum of Aurora does occur at the beginning of a 
nearly three-month's minimum of Lightning, and corresponds rather to the period of 
dry North- East winds. 

So that on the whole, Aurora and Lightning, noth withstanding that they may both 
claim electricity in large part for their luminous manifestations, are left by meteorology 
at singular points of variance with each other, just as spectroscopic analysis declares their 
molecular constitution entirely different. 

Thus far all these preceding 20 Tables of 32 years' collection are the continuation of the 
older 20 tables of the first 16 years, under the same titles and the same numbers. But 
before we introduce their summings up for one mean epoch of time, as was done in the 
old Table XXL, to be re-introduced presently as Table XXXI. , — let us describe the new 
Tables already alluded to, and to be numbered from XXI. to XXX. inclusive. 

3. Newly prepared Tables for New Derivations from the Old Observational 

Meteorology. 

Thus of the new Tables XXL and XXII., the former of the Mean monthly Maxima, 
and the latter of the Mean monthly Minima, of Temperature in the shade, — it should be 



MEAN SCOTTISH METEOROLOGY. 273 

explained that they are prepared to satisfy a want, often expressed in public, as to having 
these extreme quantities, or limits in either direction for the daily cycle of that kind of 
temperature clearly set before the eye, without giving the head of the reader the trouble 
of deducing them by simple arithmetic from the old Tables III. and IV. Where Table III. 
is the mean Temperature of the 24 hours in the shade, and Table IV. the daily cycle or range 
of differences of the said shade Temperature in the same length of time. One half therefore 
of this latte